Chapter 16. The Shoulder

At the completion of this chapter, the reader will be able to:

1. Describe the anatomy of the joints, ligaments, muscles, blood, and nerve supply that comprise the shoulder complex.

2. Describe the biomechanics of the shoulder complex, including the open- and close-packed positions, muscle force couples, and the static and dynamic stabilizers.

3. Describe the relationship between muscle imbalance and functional performance of the shoulder.

4. Describe the purpose and components of the tests and measures for the shoulder complex.

5. Perform a comprehensive examination of the shoulder complex, including history, systems review, palpation of the articular and soft tissue structures, specific passive mobility tests, passive articular mobility tests, and special tests.

6. Evaluate the key findings from the examination data to establish a physical therapy diagnosis and prognosis.

7. Summarize the various causes of shoulder dysfunction.

8. Describe and demonstrate intervention strategies and techniques based on the clinical findings and any established goals.

9. Evaluate the intervention effectiveness to determine progress and modify an intervention as needed.

10. Plan an effective home program and instruct the patient in its use.

The shoulder is the most rewarding joint in the body because when a limited or painful movement is found, the finding is seldom ambiguous and often implicates the offending structure.

— James Cyriax, MD (1904–1985)

The primary function of the shoulder complex is to position the hand in space, thereby allowing an individual to interact with his or her environment and to perform fine motor functions. An inability to position the hand results in profound impairment of the entire upper extremity. 1

Secondary functions of the shoulder complex include the following:

• Suspending the upper limb.
• Providing sufficient fixation so that motion of the upper extremity or trunk can occur.
• Serving as a fulcrum for arm elevation. Three types of arm elevation are recognized: an upward motion of the upper extremity in the scapular plane ( scaption) and the motions in either the coronal plane ( abduction) or in the sagittal plane ( flexion).

The shoulder is endowed with a unique blend of mobility and stability. The degree of mobility is contingent on a healthy articular surface, intact muscle–tendon units, and supple capsuloligamentous restraints. The degree of stability is dependent on intact capsuloligamentous structures, proper function of the muscles, and the integrity of the osseous articular structures. 1Optimal functioning of the shoulder and arm can only take place if a delicate balance between mobility and stability is maintained.

The shoulder complex functions as an integrated unit, involving a complex relationship between its various components. The components of the shoulder joint complex consist of ( Fig. 16-1):

• three bones (the humerus, the clavicle, and the scapula);
• three joints (the sternoclavicular (S-C), the acromioclavicular (A-C), and the glenohumeral (G-H) joints);
• one “pseudojoint” (the articulation between the scapula and the thorax);
• one physiological area (the suprahumeral or subacromial space).

For optimal function to occur at the shoulder, motion also has to be available at the cervicothoracic junction and at the connections between the first three ribs and the sternum and spine.

The G-H joint is a true synovial-lined diarthrodial joint that connects the upper extremity to the trunk, as part of the upper kinetic chain. The G-H joint is described as a ball and socket joint—the humeral head forms roughly half a ball or sphere ( Fig. 16-1), whereas the glenoid fossa forms the socket.

The head of the humerus faces medially, posteriorly, and superiorly with the axis of the head forming an angle of 130–150 degrees with the long axis of the humerus. 2In the frontal plane, the head of the humerus is angled posteriorly (retroverted) by 30–40 degrees. 3, 4The joint capsule of the G-H joint is lax inferiorly to permit full elevation of the arm.

The glenoid fossa of the scapula faces laterally, superiorly, and anteriorly at rest and inferiorly and posteriorly when the arm is in the dependent position ( Fig. 16-2). 5The glenoid fossa is flat and covers only one-third to one-fourth of the surface area of the humeral head. This arrangement allows for a great deal of mobility but little in the way of articular stability ( Fig. 16-3). However, the glenoid fossa is made approximately 50% deeper (doubling the depth of the glenoid fossa across its equatorial line) 6and more concave by a ring of fibrous cartilage 7and dense fibrous collagen8called a labrum. The labrum forms a part of the articular surface and is attached to the margin of the glenoid cavity and the joint capsule. 9It is also attached to the lateral portion of the biceps anchor superiorly. 10In addition, approximately 50% of the fibers of the long head of the biceps (LHB) brachii originate from the superior labrum (the remainder originates from the superior glenoid tubercle), 8with four different variations identified, 11and continue posteriorly to become a periarticular fiber bundle, making up the bulk of the labrum. 10, 12The labrum enhances joint stability by increasing the humeral head contact areas to 75% vertically and 56% transversely. 5, 9The humeral–glenoid contact area provides two primary functions 13: it spreads the joint loading over a broad area, and it permits movement of opposing joint surfaces with minimal friction and wear. 14However, because the humeral head is larger than the glenoid, at any point during elevation, only 25–30% of the humeral head is in contact with the glenoid, with the greatest contact occurring during elevation rather than at the extremes. Contact between the humeral head and glenoid fossa is significantly reduced when the humerus is positioned in 15– 17

• adduction, flexion, and internal rotation (IR);
• abduction and elevation;
• adducted at the side, with the scapula rotated downward.

Although the labrum provides some stability for the G-H joint, additional support is provided by both dynamic and static mechanisms. The dynamic mechanisms include the muscles of the rotator cuff (supraspinatus, infraspinatus, teres minor, and subscapularis muscles) ( Fig. 16-4) and a number of muscle force couples described later. The static mechanisms, which include reinforcements of the joint capsule, joint cohesion and geometry, and ligamentous support, are also described later.

The scapula ( Fig. 16-1) functions as a stable base from which G-H mobility can occur. The scapula is a flat blade of bone that is oriented to contribute to stability: it lies along the thoracic cage at 30 degrees to the frontal plane, 3 degrees superiorly relative to the transverse plane to augment functional reaching motions above shoulder height, 18and 20 degrees forward in the sagittal plane. 19– 21This orientation results in arm elevation occurring in a plane that is 30–45 degrees anterior to the frontal plane. When elevation of the arm occurs in this plane, the motion is referred to as scapular plane abductionor scaption.

The scapula's wide and thin configuration allows for its smooth gliding along the thoracic wall and provides a large surface area for muscle attachments both distally and proximally. 24In all, 16 muscles gain attachment to the scapula ( Table 16-1). Six of these muscles, including the trapezius, rhomboids, levator scapulae, and serratus anterior, support and move the scapula, while nine of the others are concerned with G-H motion. 25– 27

Posteriorly, the scapula is divided by the elevated scapula spine into two unequally sized muscle compartments. The supraspinous fossa is small and serves as the site of origin for the supraspinatus muscle (see Fig. 16-4). The infraspinous fossa gives attachment for the downward-acting infraspinatus and teres minor muscles, important muscles for the stabilization of the humeral head (see “Muscles of the Shoulder Complex”section). The spine of the scapula (see Fig. 16-1) provides a continuous line of attachments for the supporting trapezius muscle along its upper border, whereas the deltoid muscle, which suspends the humerus, gains origin from its lower border. The undersurface of the scapula is covered by the subscapularis muscle, which also assists in stabilizing the humeral head against the glenoid fossa.

A prominent feature of the scapula is the large overhanging acromion (see Fig. 16-3), which, along with the coracoacromial ligament and the previously mentioned labrum, functionally enlarges the G-H socket. The position of the acromion also places the deltoid muscle in a dominant position to provide muscular support during elevation of the arm. Bigliani et al. 21, 28introduced the following acromion types:

• Type I has a relatively flat undersurface
• Type II is slightly convex
• Type III is hooked

The distance, or angle, between the scapula and the clavicle is variable and depends on function. While the shoulder is protracted, the angle is 50 degrees. At rest, the angle is approximately 60 degrees, and with retraction the angle increases to 70 degrees. 3

Along the medial border of the scapula arise three muscles: the two rhomboid muscles and the serratus anterior ( Fig. 16-5), all of which aid with scapular stability during arm elevation (see later). The coracoid process (see Fig. 16-3) projects forward like a crow's beak, for which it is named. This forward position provides an efficient lever whereby the small pectoralis muscle can help to stabilize the scapula. In addition, the process serves as a point of origin for the coracobrachialis and the short head of the biceps muscle.

The lateral attachment of the voluminous joint capsule of the G-H joint attaches to the anatomical neck of the humerus ( Fig. 16-6). 6Medially, the capsule is attached to the periphery of the glenoid and its labrum. The overall strength of the joint capsule bears an inverse relationship with the patient's age; the older the patient, the weaker the joint capsule. The fibrous portion of the capsule is very lax and has several recesses, depending on the position of the arm. At its inferior aspect, the capsule forms an axillary recess, which is both loose and redundant. The recess permits normal elevation of the arm, although it can also be the site of adhesions when the shoulder is immobilized in adduction. The anterior aspect of the joint capsule is reinforced by three ligaments (Z ligaments), which are described in the next section. The tendons of the rotator cuff (supraspinatus, infraspinatus, teres minor, and subscapularis) reinforce the superior, posterior, and anterior aspects of the capsule, as does the LHB tendon.

An inner synovial membrane lines the fibrous capsule and secretes synovial fluid into the joint cavity. The synovium typically lines the joint capsule and extends from the glenoid labrum down to the neck of the humerus. It also forms variously sized bursae, the largest of which, the subacromial or subdeltoid bursa, lies on the superior aspect of the joint (see later).

The greater and lesser tuberosities (see Fig. 16-1), which serve as attachment sites for the tendons of the rotator cuff muscles, are located on the lateral aspect of the anatomical neck of the humerus, an imaginary line that separates the humeral head from the rest of the humerus. The lesser tuberosity serves as the attachment for the subscapularis. The greater tuberosity serves as the attachment for the supraspinatus, infraspinatus, and teres minor. The greater and lesser tuberosities are separated by the intertubercular groove (see Fig. 16-1), through which passes the tendon of the LHB on its route to attach to the superior rim of the glenoid fossa. This groove has wide variance in the angle of its walls, but 70% fall within a 60–75-degree range. 30Certain shoulder disorders, including rotator cuff and bicipital tendinitis, have been associated with anomalies of this groove. 31As the tendon of the LHB ( Fig. 16-7) passes over the humeral head from its origin, it makes a right-angle turn to lie in the anterior aspect of the humerus. This abrupt turn may permit abnormal wearing of the tendon at this point. The roof of this groove is formed by the transverse ligament. The transverse humeral ligament ( Fig. 16-7), which runs perpendicular over the biceps tendon, was once thought to function as a restraint to the biceps tendon within the intertubercular groove. However, this appears to be the role of the coracohumeral ligament. 31

The region below the greater and lesser tuberosities, where the upper margin of the humerus joins the shaft of the humerus, is referred to as the surgical neck ( Fig. 16-1). The axillary nerve and posterior humeral circumflex artery lie in close proximity to the medial aspect of the surgical neck.

Ligaments

A number of structures function as static stabilizers during motion of the arm to reciprocally tighten and loosen, thereby limiting translation and rotation of the G-H joint surfaces in a load-sharing fashion. 32These include the G-H ligaments and the posterior capsule. Further static stabilization is provided by the glenoid labrum. The posterior capsule is under tension when the shoulder is in flexion, abduction, IR (in particular, the superior and middle segments), or in any combination of these.

At the anterior portion of the outer fibers of the joint capsule, three local reinforcements are present: the superior, middle, and inferior G-H ligaments ( Fig. 16-6). Together with the coracohumeral ligament, these ligaments form a Z-pattern on the anterior aspect of the shoulder ( Fig. 16-6). 33In the midrange of rotation, the G-H ligaments are relatively lax and stability is maintained primarily by the action of the rotator cuff muscle group compressing the humeral head into the conforming glenoid articulation. 32The G-H ligaments appear to produce a major restraint during shoulder flexion, extension, and rotation 34:

• The anterior G-H ligament is under tension when the shoulder is in extension, abduction, and/or external rotation (ER).
• The posterior G-H ligament is under tension in flexion and ER.
• The inferior G-H ligament is the most important of the G-H ligaments. It is under tension when the shoulder is abducted, extended, and/or externally rotated. In addition, this ligament is a primary restraint against both anterior and posterior dislocations of the humeral head, and is the most important stabilizing structure of the shoulder in the overhead athlete. 35At 0-degree abduction, the subscapularis muscle, the labrum, and the superior G-H ligament are the primary restraints against anterior translation. At 45-degree abduction, the subscapularis muscle and the middle and inferior G-H ligaments, along with labrum, prevent anterior translation. When the arm is abducted more than 90 degrees, which is the most common position of anterior dislocation, the anterior fibers of the inferior G-H ligament are the primary restraint anterior movement. 9, 36
• The middle G-H ligament is under tension when the shoulder is flexed and externally rotated. In addition, the middle G-H ligament and the subscapularis tendon limit ER from 45 to 75 degrees of abduction, and are important anterior stabilizers.

Other ligaments ( Fig. 16-6) help provide stability to the G-H joint. These include the following:

• The coracohumeral ligament.The coracohumeral ligament (see Fig. 16-6) arises from the lateral end of the coracoid process and runs laterally, where it is split into two bands by the presence of the biceps tendon. The posterior band blends with the supraspinatus tendon to insert near the greater tuberosity, and the anterior band blends with the subscapularis tendon to insert near the lesser tuberosity. The coracohumeral ligament covers the superior GH ligament anterosuperiorly and fills the space between the tendons of the supraspinatus and subscapularis muscles, uniting these tendons to complete the rotator cuff in this area. Tears of the cuff usually extend longitudinally between the supraspinatus and coracohumeral ligament so that the hood action of the cuff is lost. It is generally agreed that the posterior band of the coracohumeral ligament limits flexion, whereas the anterior band limits extension of the G-H joint. 37Both the bands also limit inferior and posterior translation of the humeral head, strengthening the superoanterior aspect of the capsule. 37, 38
• The coracoacromial ligament.The coracoacromial ligament (see Fig. 16-6) is often described as the roof of the shoulder. It is a very thick structure that runs from the coracoid process to the anteroinferior aspect of the acromion, with some of its fibers extending to the A-C joint. The ligament consists of two bands that join near the acromion, and it is ideally suited, both anatomically and morphologically, to prevent separation of the A-C joint surfaces. The coracoclavicular ligaments and the costoclavicular ligament are described in the A-C joint section and the S-C joint section, respectively.

Coracoacromial Arch

The coracoacromial arch ( Fig. 16-6) is formed by the anteroinferior aspect of the acromion process, and the coracoacromial ligament, which connects the coracoid to the acromion and the inferior surface of the A-C joint. 39– 41A number of structures are located in the subacromial space ( Fig. 16-7) between the coracoacromial arch superiorly and the humeral head inferiorly, and the coracoid process, anteromedially. These include (from inferior to superior) the following:

• the head of the humerus,
• the long head of biceps tendon (intra-articular portion),
• the superior aspect of the joint capsule,
• the supraspinatus and upper margins of subscapularis and infraspinatus,
• the subdeltoid–subacromial bursae,
• the inferior surface of coracoacromial arch.

In normal individuals, the suprahumeral space averages 10–11 mm in height with the arm adducted to the side. 42, 43Elevating the arm decreases this space, and the space is at its narrowest between 60 and 120 degrees of scaption. 44During overhead motion in the plane of the scapula, the supraspinatus tendon, the region of the cuff most involved in overuse syndromes of the shoulder, can pass directly underneath the coracoacromial arch. If the arm is elevated while internally rotated, the supraspinatus tendon passes under the coracoacromial ligament, whereas if the arm is externally rotated, the tendon passes under the acromion itself. 45

Muscle imbalances or capsular contractures can cause an increase in superior translation of the humeral head, narrowing the subacromial space. For example, if the rotator cuff muscles are weak or injured, increased translation occurs between the humeral head and the glenoid labrum. 46This increase in translation may lead to increased wear on the labrum, increased reliance on the static restraints (e.g., ligaments, capsule), and eccentric overloading of the dynamic (muscle) restraints, which in turn can result in instability and/or a condition termed “subacromial impingement syndrome (SIS).” 47, 48

Bursae

Approximately eight bursae are distributed throughout the shoulder complex. The subdeltoid–subacromial bursae (see Fig. 16-7) are collectively referred to as the subacromial bursa because they are often continuous in nature. The subacromial bursa is one of the largest bursae in the body and provides two smooth serosal layers, one of which adheres to the overlying deltoid muscle and the other to the rotator cuff lying beneath. This bursa is also connected to the acromion, greater tuberosity, and coracoacromial ligament. As the humerus elevates, it permits the rotator cuff to slide easily beneath the deltoid muscle. There are also smaller bursae interposed between most of the muscles in contact with the joint capsule:

• The subcoracoid bursa.This bursa is located under the coracoid process.
• The subscapular bursa.This bursa is located between the subscapular muscle tendon and the anterior neck of the scapula and protects the tendon as it passes under the coracoid process.

Neurology

The shoulder complex is embryologically derived from C5 to C8, except the A-C joint, which is derived from C4 ( Fig. 16-8). The sympathetic nerve supply to the shoulder originates primarily in the thoracic region from T2 down as far as T8. 49

One study 50attempted to determine the variability of the course and the pattern of these nerves and found that the peripheral nerves contributing to the anterior shoulder joint included the axillary (C5–6), subscapular (C5–6), and lateral pectoral (C5–6). The same study found that the nerves contributing articular branches to the posterior joint structures are the suprascapular nerve (C5–6) and small branches of the axillary nerve. 50The pathways of these nerves are described in Chapter 3.

Other nerves innervate the muscles that act upon the shoulder. These include the long thoracic nerve (C5–7), which innervates the serratus anterior, the spinal accessory nerve (cranial nerve XI and C3–4), which innervates the sternocleidomastoid (SCM) and trapezius muscles, and the musculocutaneous nerve (C5–7), which innervates the coracobrachialis, biceps brachii, and brachialis, before dividing into its cutaneous branches.

Vascularization

The vascular supply to the shoulder complex is primarily provided by branches off the axillary artery ( Fig. 16-9), which begins at the outer border of the first rib as a continuation of the subclavian artery. The axillary artery is commonly divided into three parts: above, behind, and below the pectoralis minor muscle. The axillary artery meets the more deeply placed brachial plexus in the neck, and here they are encased in the axillary sheath, together with the axillary vein. 53The lateral, posterior, and medial cords of the brachial plexus descend behind the first portion of the artery and then take up their respective locations at the second portion of the artery (behind the pectoralis minor muscle). The branches off these cords also maintain their respective positions. Compression of the axillary artery (or, to a lesser degree, the axillary vein) can result in shoulder dysfunction and most commonly occurs in the posterior fossa around the shoulder and against the humerus with shoulder elevation. 53The G-H joint receives its blood supply from the anterior and posterior circumflex humeral as well as the suprascapular and circumflex scapular vessels. 54The vascular supply to the labrum arises mostly from its peripheral attachment to the capsule and is from a combination of the suprascapular circumflex scapular branch of the subscapular and posterior circumflex humeral arteries. 8

The brachial artery provides the dominant arterial supply to each of the two heads of the biceps brachii. The artery travels in the medial intermuscular septum and is bordered by the biceps muscle anteriorly, the brachialis muscle medially, and the medial head of the triceps muscle posteriorly. 55

The microvasculature of the rotator cuff has been the subject of much discussion and consists of three main sources: the thoracoacromial, suprahumeral, and subscapular arteries. 54The supraspinatus receives its primary supply from the thoracoacromial arteries. The subscapularis receives its supply from the anterior humeral circumflex and the thoracoacromial arteries. The posterior rotator cuff muscles, the infraspinatus and teres minor, receive their blood supply from the posterior humeral circumflex and suprascapular artery. The circulation of the rotator cuff is unidirectional with no flow traversing the tide mark at the insertion of the supraspinatus. 56The supraspinatus and biceps tendons appear to be particularly vulnerable to areas of relative avascularity, referred to as critical zones. The vascular compromise of the supraspinatus is thought to be due to a number of factors:

• It can be directly compressed by the subacromial structures. With the arm adducted to the side, the vessels within the supraspinatus tendon are poorly perfused. 57Other arm positions, such as raising the arm above 30 degrees, have been shown to increase intramuscular pressure in the supraspinatus muscle to an extent that may impair normal blood perfusion. 57, 58
• Its blood vessels travel parallel to the tendon fibers, which make them vulnerable to stretch. 59Avascularity appears to increase with age beginning as early as 20 years. 60
• The presence of a critical zone just proximal to the supraspinatus insertion point. 57Two early studies noted a critical zone that lies slightly proximal to the supraspinatus insertion point. 61, 62Since then, it has been determined that the critical zone is more likely a zone of anastomoses between the vessels supplying the bone and the tendon and is not less vascular except in certain positions. 57, 63, 64

Although it is possible that sustained isometric contractions, prolonged adduction of the arm or increase in subacromial pressure 65may reduce the microcirculation, it is unlikely that frequent abduction or elevation of the arm would produce selective avascularity of the supraspinatus or biceps tendon.

Close-Packed Position

The close-packed position for the G-H joint is 90 degrees of G-H abduction and full ER or full abduction and ER, depending on the source.

Open-Packed Position

Without IR or ER occurring, the open-packed position of the G-H joint has traditionally been cited as 55 degrees of semiabduction and 30 degrees of horizontal adduction. 66More recently, a cadaver study, which examined the point in the range at which maximal capsular laxity occurred in seven subjects, determined the open-packed position to be 39 degrees of abduction in the scapular plane or at the point which is 45% of the maximal available abduction range of motion (ROM). 67This finding suggests that the open-packed position may be closer to neutral and that joint mobility testing and joint mobilizations of the G-H joint should be initiated according to a smaller angle of abduction than the traditionally cited open-packed position. 67

The zero position for the G-H joint is the arm relaxed by the side, which, relative to the scapula, averages approximately 0 degree of abduction, 12 degrees of flexion, and 10 degrees of ER. 68

Capsular Pattern

According to Cyriax, 69the capsular pattern for the G-H joint is that ER is the most limited, abduction the next most limited, and IR the least limited in a 3:2:1 ratio, respectively. However, this pattern only appears to be consistent with adhesive capsulitis of the shoulder. IR, rather than ER or abduction, appears to be the most limited motion in conditions with selected capsular hypomobility. 70

The A-C joint is a diarthrodial joint, formed by the medial margin of the acromion and the lateral end of the clavicle. The A-C joint is most often described as a gliding or plane joint, but the joint surfaces can vary from flat to slightly convex or concave, corresponding with the articulating surface of the acromion. In the early stages of development, the articular surfaces of the A-C joint are lined with hyaline cartilage, which changes to fibrocartilage at approximately 17 years of age on the acromial side of the joint, and until approximately 24 years of age on the clavicular side. 71Within the A-C joint, there is variable presence of a thumbtack-shaped intra-articular fibrous disk that projects superiorly into, and incompletely divides, the A-C joint. This disk is subject to tearing. 71When viewed from above, the clavicle is convex anteriorly in the medial two-thirds and convex posteriorly in the lateral one-third (see Fig. 16-1). Variability in the inclination of the joint is common and can be anywhere from 10 to 50 degrees, but the anteromedial border of the acromion usually faces anteriorly, medially, and superiorly. 72This variability may account for the differences in vulnerability to separation seen among people. 73

The A-C joint serves as the main articulation that suspends the upper extremity from the trunk, and it is at this joint about which the scapula moves. The clavicle serves as the lever by which the upper extremity acts on the torso and as an attachment site for many soft tissues. 71, 74The joint has a thin capsule lined with synovium, which is strengthened anteriorly, posteriorly, inferiorly and superiorly by A-C ligaments (see Fig. 16-6). The superior A-C ligament (see Fig. 16-6) gives support to the capsule and serves as the primary restraint to posterior translation and posterior axial rotation at the joint. 71Other support structures for the joint include the costoclavicular, coracoclavicular (conoid and trapezoid) ligament, the pectoralis major, SCM, deltoid, and trapezius muscles (see Fig. 16-10). 74, 75

Ligaments

The coracoclavicular ligament (conoid and trapezoid portions) (see Fig. 16-6) is the primary support for the A-C joint and runs from the coracoid process to the inferior surface of the clavicle. The conoid ligament (see Fig. 16-6) is fan shaped with its apex pointing inferiorly. It lies in the frontal plane and is the more medial of the two ligaments. This ligament functions to block coracoid movement away from the clavicle inferiorly. 78The trapezoid ligament arises from the medial border of the upper surface of the coracoid process and runs superiorly and laterally to insert into the inferior surface of the clavicle. It is larger, longer, and stronger than the conoid and forms a quadrilateral sheet that lies in a plane that is at right angles to the plane formed by the conoid ligament. The function of this ligament is unclear, although its orientation suggests that it may block medial movement of the coracoid 78or act as a restraint to superior or posterior displacement of the clavicle. 79In addition, as the clavicle rotates upward, the coracoclavicular ligament dictates scapulothoracic rotation by virtue of its attachment to the scapula. 80

Neurology

Innervation to this joint is provided by the suprascapular, lateral pectoral, and axillary nerves ( Fig. 16-8). 82

Vascularization

The A-C joint receives its blood supply from branches of the suprascapular and thoracoacromial arteries ( Fig. 16-9).

Capsular Pattern

Joints such as the A-C joint, which are not controlled by muscles, lack true capsular patterns. However, anecdotal clinical evidence suggests that the capsular pattern for the A-C joint is pain at the extremes of ROM, especially horizontal adduction and full elevation.

Close-Packed Position

The close-packed position for this joint is probably only achievable in the below-30 age group and clinically seems to correspond to 90 degrees of G-H joint abduction.

Open-Packed Position

The open-packed position for this joint is undetermined, although it is likely to be when the arm is by the side. This positions the clavicle in approximately 15–20 degrees of retraction relative to the coronal plane and elevated approximately 2 degrees from the horizontal plane. 83

The motions available at the A-C joint occur around three axes:

• Rotation in an anteroposterior (A-P) direction around a longitudinal axis that projects through the A-C and S-C joints, and rotation in a superoinferior (vertical) direction. The A-P rotation occurs during arm elevation. The superoinferior rotation, which occurs around the costoclavicular ligament, is involved during protraction (anterior movement of the acromial end of the clavicle) and retraction (posterior motion of the acromial end). The A-P rotation of the clavicle on the scapula is three times greater than that of the superoinferior rotation. The clavicle can rotate approximately 30–50 degrees in the A-P direction, most of which is contributed by the mobile S-C joint. The A-C joint only contributes approximately 5–8 degrees to the rotation. 84The type of glide and rotation that occurs with clavicular motion depends on the shoulder motion and the shape of the articular surfaces. If the lateral end of the clavicle presents a concave surface, an anterior glide is combined with an anterior rotation. If the lateral end presents a convex surface, an anterior glide is combined with a posterior rotation.

• Pure spin/rotation. A pure spin occurs during abduction/adduction (lateral and medial rotation of inferior scapula angle) motions.
• Glides. Glides of the clavicle can occur in an A-P and superoinferior direction.

The A-C joint is predisposed to chronic stress injury, especially in the situations in which it is subjected to repetitive high demand. 71, 85The joint can also be affected by direct trauma and by nontraumatic factors such as degenerative arthritis and inflammatory arthropathies. 74Table 16-2contains the pathologies and dysfunctions that may affect the A-C joint.

The S-C joint represents the articulation between the enlarged medial end of the clavicle, the clavicular notch of the manubrium of the sternum, and the cartilage of the first rib, which forms the floor of the joint. The articulating surfaces of the S-C joint are covered with fibrocartilage. The S-C joint is angulated slightly upward approximately 20 degrees in a posterior and lateral direction. The clavicle presents with an irregularly shaped surface to the meniscus, and this lateral part of the joint acts as an ovoid. If held vertically, the proximal end of the clavicle is convex whereas the manubrium surface is concave (see Fig. 16-1). If held anteroposteriorly, the proximal end of the clavicle is concave and the manubrium is convex. A very thick meniscus is the key to the joint curvature. The disk is attached to the upper and posterior margin of the clavicle, and to the cartilage of the first rib by an intra-articular disk ligament, which functions to help prevent medial displacement of the clavicle, and completely divides the joint into two cavities: a larger one that is above and lateral to the disk, and a smaller one that is medial and below the disk. Greater movement occurs between the clavicle and the disk than between the disk and the manubrium. The S-C joint has very little bony stability and relies heavily on support from the surrounding capsule and ligaments.

Some confusion seems to exist about classification of the S-C joint—it has been classified as a ball and socket joint, 82a plane joint, 86and as a saddle joint. 82These classifications depend on whether anatomy or function is being considered. For example, when its function is considered, the S-C joint acts similar to a ball and socket joint, allowing for motion in almost all planes, including rotation.

Ligaments

Because of its bony arrangement, the S-C joint itself is extremely weak, but is held securely by strong ligaments that hold the sternal end of the clavicle downward and toward the sternum. These ligaments include the following:

Capsular-Ligamentous Structures

Capsular Ligament

This ligament represents the inner aspect of the joint capsule. The anterior portion is heavier and stronger, and it covers the anterior aspect of the joint running obliquely from the proximal end of the clavicle to the sternum in an inferior and medial direction. The posterior component, which covers the posterior aspect of the joint, also runs obliquely from the proximal end of the clavicle to the sternum in an inferior and medial direction. The capsular ligament is considered the most important and strongest ligaments of the S-C joint and is most responsible for preventing upward displacement of the medial clavicle in the presence of a downward force on the distal end of the shoulder. 88

Interclavicular

This ligament connects the superomedial sternal ends of each clavicle with the capsular ligaments and the upper sternum. Together, these structures help to hold up the shoulder. This function can be demonstrated by placing a finger in the superior sternal notch; the ligament is lax with elevation of the arm but becomes taut when both arms are hanging by the sides.

Costoclavicular (Rhomboid Ligament)

This short and strong ligament, which runs from the upper border of the first rib to the inferior surface of the clavicle, consists of two laminae: fibers of the anterior lamina run superiorly and laterally and check elevation and lateral movement (upward rotation) of the clavicle. 88The posterior lamina fibers run superiorly and medially and check downward rotation of the clavicle. 88

Due to the support provided by the ligaments, the S-C joint is very stable and trauma to the clavicle usually results in a fracture rather than a joint dislocation. 89Gross motions occur here as with the A-C joint. The SCM, which can be seen clearly with rotation of the head, has a tendinous sternal and clavicular insertion. The subclavius (C5–6) has a questionable function but may function as a dynamic ligament, which contracts and pulls the clavicle toward the manubrium.

Two types of translation also occur at this joint: anterior to posterior and superior to inferior, with the former exceeding the latter motion by 2:1. 90These translations allow for three degrees of freedom (DOF): the movements of elevation, depression; protraction, retraction; and upward (backward) and downward (forward) motion.

• Protraction/retraction.Approximately 15–20 degrees of protraction and retraction of the clavicle are available. With protraction, the concave surface of the medial clavicle moves on the convex sternum, producing an anterior glide of the clavicle, and an anterior rotation of the lateral clavicle. 90With retraction to the neutral position, the medial clavicle articulates with a flat surface and tilts/swings, causing an anterolateral gapping, and a posterior rotation at the lateral end. 90
• Elevation/depression of the clavicle.There are 35–40 degrees of elevation and approximately 15 degrees of depression available, 3, 87, 90involving the convex clavicle gliding on the concave sternum.

As the clavicle elevates and rolls upward on the manubrium, an inferior glide is produced, with the reverse occurring with depression. Elevation and depression movements at the S-C joint are associated with reciprocal motions of the scapula because of the lateral attachment of the clavicle to the scapula at the A-C joint. 75

Rotation around the long axis produces a spin of the clavicle on the manubrium. Approximately 40 degrees of upward rotation and 5 degrees of downward rotation are available and are necessary to allow upward scapular rotation. 3, 87

Close-Packed Position

The close-packed position for the S-C joint is maximum arm elevation and protraction.

Open-Packed Position

The open-packed position for the S-C joint has yet to be determined, but is likely to be when the arm is by the side.

Capsular Pattern

Similar to the A-C joint, the S-C joint is not controlled by muscles and therefore lacks a specific capsular pattern. One possibility, seen clinically, is pain at the extreme ranges of motion, especially full arm elevation and horizontal adduction.

Neurology

Pain can be referred from this joint to the throat, anterior chest, and axillae. The neural supply to this joint is primarily from the following 91:

• The anterior supraclavicular nerve
• The nerve to the subclavius (medial accessory phrenic) C5–6
• The T1 spinal nerve root

Vascularization

The S-C joint receives its blood supply from the internal thoracic and suprascapular arteries. 92

This articulation is functionally a joint, but it lacks the anatomic characteristics of a true synovial joint. However, the movement of the scapula on the wall of the thoracic cage is critical to shoulder joint motion. A lack of ligamentous support at this “joint” delegates the function of stability fully to the muscles that attach the scapula to the thorax.

An altered position of the scapula or an abnormal motion at this joint due to muscle imbalances have both been linked with shoulder complex dysfunction. 24, 93, 94Motions at this joint are described according to the movement of the scapula relative to the thorax. Available motion consists of approximately 60 degrees of upward rotation of the scapula, 40–60 degrees of IR/ER, and 30–40 degrees of anterior and posterior tipping of the scapula. 95Other motions occurring here include elevation and depression and adduction and abduction of the scapula ( Fig. 16-11).

Close-Packed and Capsular Pattern

Since the scapulothoracic joint is not a true joint, it does not have a close-packed position or a capsular pattern.

Open-Packed Position

Relative to the thorax, when the arm is by the side, the scapula is in an average of 30–45 degrees of IR, and slight upward rotation, and approximately 5–20 degrees of anterior tipping. 68, 95

Bursae

There are a number of bursae located in and around the scapulothoracic articulation. The scapulothoracic bursa is located between the thoracic cage and the deep surface of the serratus anterior. 96The subscapular bursa is most often located between the superficial surface of the serratus anterior and the subscapularis. 96

The scapulotrapezial bursa lies between the middle and lower trapezius fibers and the superomedial scapula. 96The purpose and clinical significance of the scapulotrapezial bursa are not known. It may encourage smooth gliding of the superomedial angle of the scapula against the undersurface of the trapezius during scapular rotation in the same manner that the scapulothoracic bursa (between the serratus attachment at the anteromedial surface of the superior angle) encourages smooth gliding against the underlying ribs. 96It is possible that inflammation of either of these bursae, directly or as a consequence of injury, may result in painful clicking at the superomedial angle of the scapula. 96

The relationship of the spinal accessory nerve to the scapulotrapezial bursa may also have clinical importance, especially as it is closely applied to the superficial wall of the scapulotrapezial bursa. 96The spinal accessory nerve receives afferent fibers from C3 and C4, which are thought to be proprioceptive, before reaching the deep surface of the trapezius. 96, 97As a consequence of their proximity, inflammation and fibrosis within the bursa may cause irritation and pain of the nerve, or interference with the normal proprioceptive feedback mechanism provided by the nerve. 96

A number of significant muscles control motion at the shoulder and provide dynamic stabilization. Rarely does a single muscle act in isolation at the shoulder. For simplicity, the muscles acting at the shoulder may be described in terms of their functional roles: scapular pivoters, humeral propellers, humeral positioners, and shoulder protectors ( Table 16-3). 98

Scapular Pivoters

The scapular pivoters comprise the trapezius, serratus anterior, levator scapulae, rhomboid major, and rhomboid minor. 98As a group, these muscles are involved with motions at the scapulothoracic articulation, and their proper function is vital to the normal biomechanics of the whole shoulder complex. The scapular muscles can contract isometrically, concentric, or eccentrically, depending on the desired action and whether the action involves stabilization, acceleration, or deceleration. To varying degrees, the serratus anterior and all parts of the trapezius cooperate during the upward rotation of the scapula.

Trapezius

The trapezius muscle ( Fig. 16-10) originates from the medial third of the superior nuchal line, the external occipital protuberance, the ligamentum nuchae, the apices of the seventh cervical vertebra, all the thoracic spinous processes, and the supraspinous ligaments of the cervical and thoracic vertebrae. The upper fibers descend to attach to the lateral third of the posterior border of the clavicle. The middle fibers of the trapezius run horizontally to the medial acromial margin and superior lip of the spine of the scapula. The inferior fibers ascend to attach to an aponeurosis gliding over a smooth triangular surface at the medial end of the spine of the scapula to a tubercle at the scapular lateral apex.

It has been suggested that the upper fibers of this muscle have a different motor supply than that to the middle and lower portions. 99, 100Recent clinical and anatomical evidence seems to suggest that the spinal accessory nerve provides the most important and consistent motor supply to all portions of the trapezius muscle, and although the C2–4 branches of the cervical plexus are present, no particular elements of innervation within the trapezius have been determined. 101

One of the functions of the trapezius is to produce shoulder girdle elevation on a fixed cervical spine. For the trapezius to perform its actions, the cervical spine must first be stabilized by the anterior neck flexors to prevent simultaneous occipital extension from occurring. Failure to prevent this occipital extension would allow the head to translate anteriorly, resulting in a decrease in the length, and therefore the efficiency, of the trapezius 102and an increase in the cervical lordosis.

Serratus Anterior

The muscular digitations of the serratus anterior (see Fig. 16-5) originate from the upper eight to ten ribs and fascia over the intercostals. The muscle is composed of three functional components 104, 105:

• The upper component originates from the first and second ribs and inserts into the superior angle of the scapula.
• The middle component arises from the second, third, and fourth ribs and inserts into the anterior aspect of the medial scapular border.
• The lower component is the largest and most powerful, originating from the fifth through ninth ribs. It runs anterior to the scapula and inserts into the medial border of the scapula.

The serratus anterior is activated with all shoulder movements, but especially during shoulder flexion and abduction. 105Working in synergy with the trapezius, as part of a force couple (see later), the main function of the serratus anterior is to protract and upwardly rotate the scapula, 106, 107while providing a strong, mobile base of support to position the glenoid optimally for maximum efficiency of the upper extremity. 108Its lower fibers draw the lower angle of the scapula forward to rotate the scapula upward while maintaining the scapula on the thorax during arm elevation. 109This moves the coracoacromial arch out of the path of the advancing greater tuberosity and opposes the excessive elevation of the scapula by the levator scapulae and trapezius muscles. 110Without upward rotation and protraction of the scapula by the serratus anterior, full G-H elevation is not possible. In fact, in patients with complete paralysis of the serratus anterior, Gregg et al. 108reported that abduction is limited to 110 degrees.

Dysfunction of the serratus anterior muscle causes winging of the scapula as the patient attempts to elevate the arm. 4, 111Scapulothoracic dysfunction can also contribute to G-H instability, as the normal stable base of the scapula is destabilized during abduction or flexion. 4, 112, 113

The serratus anterior muscle is innervated by the long thoracic nerve (C5–7).

Levator Scapulae

The levator scapulae muscle (see Fig. 16-10) originates by tendonous strips from the transverse processes of the atlas, axis, and C3 and C4 vertebrae, and descends diagonally to insert into the medial superior angle of the scapula.

The levator scapulae can act on the cervical spine (see Chap. 23) and on the scapula. If it acts on the cervical spine, it can produce extension, side flexion, and rotation of the cervical spine to the same side. 114When acting on the scapula during upper extremity flexion or abduction, the levator scapula muscle acts as an antagonist to the trapezius muscle, and provides eccentric control of scapular upward rotation in the higher ranges of motion. 115

Both the trapezius and levator scapulae muscles are activated with increased upper extremity loads. 102, 105, 116

The levator scapulae muscle is innervated by the posterior (dorsal) scapular nerve (C3–5).

Rhomboids

The rhomboid major muscle ( Fig. 16-10) originates from the second to fifth thoracic spinous processes and the overlying supraspinous ligaments. The fibers descend to insert into the medial scapular border between the root of the scapular spine and the inferior angle of the scapula.

The rhomboid minor muscle (see Fig. 16-10) originates from the lower ligamentum nuchae, and the seventh cervical and first thoracic spinous processes, and attaches to the medial border of the scapula at the root of the spine of the scapula.

The rhomboid muscles help control scapular positioning, particularly with horizontal flexion and extension of the shoulder complex. 115

The rhomboid muscles are innervated by the posterior (dorsal) scapular nerve (C4–5).

Humeral Propellers

The total muscle mass of the shoulder's internal rotators (subscapularis, anterior deltoid, pectoralis major, latissimus dorsi, and teres major) is much greater than that of the external rotators (infraspinatus, teres minor, and posterior deltoid). 103This fact explains why the shoulder internal rotators produce approximately 1.75 times greater isometric torque than the external rotators. 117Peak torques of the internal rotators also exceed the external rotators when measured isokinetically, under both concentric and eccentric conditions. 103, 118

Latissimus Dorsi

The latissimus dorsi muscle (see Fig. 16-12) originates from the spinous processes of the last six thoracic vertebrae, the lower three or four ribs, the lumbar and sacral spinous processes through the thoracolumbar fascia, the posterior third of the external lip of the iliac crest, and a slip from the inferior scapular angle. The scapular slip allows the latissimus dorsi to act at the scapulothoracic articulation. The latissimus dorsi inserts into the intertubercular sulcus of the humerus. The muscle functions as an extensor, adductor, and powerful internal rotator of the shoulder, and also assists in scapular depression, retraction, and downward rotation. 119It is innervated by the thoracodorsal nerve (C6–8).

Teres Major

The teres major (see Fig. 16-12) originates from the inferior third of the lateral border of the scapula and just superior to the inferior angle. The teres major tendon inserts into the medial lip of the intertubercular groove of the humerus. The teres major functions to complement the actions of the latissimus dorsi in that it extends, adducts, and internally rotates the G-H joint. It is innervated by the lower subscapular nerve (C5, C6).

Pectoralis Major

The pectoralis major (see Fig. 16-13) originates from the sternal half of the clavicle, half of the anterior surface of the sternum to the level of the sixth or seventh costal cartilage, the sternal end of the sixth rib, and the aponeurosis of the obliquus externus abdominis. The fibers of the pectoralis major converge to form a tendon that inserts into the lateral lip of the intertubercular sulcus of the humerus. Although this muscle does not insert into the scapula, it does act upon the scapulothoracic articulation through its insertion on the humerus. The function of the pectoralis muscle depends on which fibers are activated:

• Upper fibers (clavicular head)—IR, horizontal adduction, flexion, abduction (once the humerus is abducted 90 degrees, the upper fibers assist in further abduction), and adduction (with the humerus below 90 degrees of abduction) of the G-H joint.
• Lower fibers (sternal head)—IR, horizontal adduction, extension, and adduction of the G-H joint.

The pectoralis major is innervated by the medial (lower fibers) and lateral (upper fibers) pectoral nerves (C8–T1 and C5–7, respectively).

Pectoralis Minor

The pectoralis minor (see Fig. 16-9) originates from the outer surface of the upper margins of the third to fifth ribs near their cartilage. The fibers of the pectoralis minor ascend laterally, converging to a tendon that inserts into the coracoid process of the scapula.

The pectoralis minor muscle is innervated by the medial pectoral nerve (C6–8).

Humeral Positioners

Deltoid

The deltoid muscle originates from the lateral third of the clavicle, the superior surface of the acromion, and the spine of the scapula ( Fig. 16-13). It inserts into the deltoid tuberosity of the humerus. The deltoid can be described as three separate muscles—anterior, middle, and posterior—all of which function as humeral positioners, positioning the humerus in space. 98

The deltoid muscle is innervated by the axillary nerve (C5–6).

Shoulder Protectors

Rotator Cuff

The rotator cuff muscles ( Fig. 16-4), which consist of the supraspinatus, infraspinatus, teres minor, and subscapularis, are commonly involved with shoulder pathology. The anatomy of these muscles was described previously (see “Glenohumeral Joint”section). These muscles are referred to as the protectors of the shoulder since, in addition to actively moving the humerus, they fine-tune the humeral head position during arm elevation. 98Compared with most joints that have a single axis on which torques are generated, the shoulder is very different, because it has no fixed axis. As a result, each muscle activation creates a unique set of rotational moments, which necessitates precise coordination in the timing and magnitude of muscle contractions. 73Jenp et al. 120used electromyography (EMG) to detect the most specific positions of highest activation for the individual rotator cuff muscles. The greatest activation of the subscapularis was with the arm in the scapular plane at 90 degrees of elevation and neutral humeral rotation. The subscapularis has also been shown to be an effective humeral head depressor in ER, whereas it produces almost no A-P translation in abduction and ER. The infraspinatus–teres minor muscles are very effective humeral head depressors with the arm in the sagittal plane and the humerus elevated to 90 degrees in the midrange of external/IR (the so-called “hornblower's” position). The supraspinatus could not be effectively isolated.

The rotator cuff muscles have an important role in the function of the shoulder and serve the following:

• Assist in the rotation of the shoulder and arm.At the G-H joint, elevation through abduction of the arm ( Table 16-4) requires that the greater tuberosity of the humerus pass under the coracoacromial arch. For this to occur, the humerus must externally rotate, and the acromion must elevate. 121ER of the humerus is produced actively by a contraction of the infraspinatus and teres minor, and by a twisting of the joint capsule. A force couple exists in the transverse plane between the subscapularis anteriorly and the infraspinatus and teres minor posteriorly in which cocontraction of the infraspinatus, teres minor, and subscapularis muscles both depresses and compresses the humeral head during overhead movements.

However, in clinical practice, shoulders having large rotator cuff tears and good function are frequently encountered. In the coronal plane, there is another force couple between the deltoid and the inferior rotator cuff muscles (infraspinatus, subscapularis, and teres minor). With the arm fully adducted, contraction of the deltoid produces a vertical force in a superior direction, resulting in an upward translation of the humeral head relative to the glenoid. Cocontraction of the inferior rotator cuff muscles produces both a compressive force and a downward translation of the humerus that counterbalances the force of the deltoid, thereby stabilizing the humeral head.

EMG studies have shown that during casual elevation of the arm in normal shoulders, the deltoid and the rotator cuff act continuously throughout the motion of abduction, each reaching a peak of activity between 120 and 140 degrees of abduction. 13, 122However, during more rapid and precise movements, such as those involved with throwing, a more selective pattern emerges with specific periods of great intensity. 123Weakening of the rotator cuff appears to allow the deltoid to elevate the proximal part of the humerus in the absence of an adequate depressor effect from the rotator cuff, resulting in a decrease in the subacromial space and impingement of the rotator cuff on the anterior aspect of the acromion. 124, 125

• Reinforce the G-H capsule.The rotator cuff muscles, together with the coracohumeral ligament, and the LHB (often referred to as the fifth rotator cuff muscle) function as contractile ligaments. For example, firing of the rotator cuff muscles increases the tension of the middle G-H ligament when the arm is abducted to 45 degrees and externally rotated. 37
• Control much of the active arthrokinematics of the GH joint.Contraction of the horizontally oriented supraspinatus produces a compression force directly into the glenoid fossa. 124This compression force holds the humeral head securely in the glenoid cavity during its superior roll, which provides stability to the joint and also maintains a mechanically efficient fulcrum for elevation of the arm. 124In the shoulder midrange position, when all of the passive restraints are lax, joint stability is achieved almost entirely by the rotator cuff. In addition, as previously mentioned, without adequate supraspinatus force, the near vertical line of force of a contracting deltoid tends to jam or impinge the humeral head superiorly against the coracoacomial arch. 103

Long Head of the Biceps Brachii

The biceps brachii muscle is a large fusiform muscle in the anterior compartment of the upper extremity, which has two tendinous origins from the scapula ( Fig. 16-7). The medial head and LHB normally originate from the coracoid process and supraglenoid tubercle of the scapula, respectively. However, a great deal of research has noted that the origin of the biceps tendon varies, not only in the type of insertion (single, bifurcated, or trifurcated), but also in the specific anatomical location where it inserts. 11, 73The proximal LHB tendon receives an arterial supply from labral branches of the suprascapular artery. 126As it leaves its origin, the LHB tendon is surrounded by a synovial sheath, which ends at the distal end of the bicipital groove, making the tendon an intra-articular but extrasynovial structure. 73As the LHB tendon moves between the greater and lesser tuberosities, it is stabilized in position by the tendoligamentous sling comprising the coracohumeral ligament, superior G-H ligament, and fibers from the supraspinatus and the subscapularis. 73, 127Once in the bicipital groove, the LHB tendon passes under the transverse humeral ligament, which bridges the groove. 128After coursing through the groove, the two heads join to form the biceps muscle belly at the level of the deltoid insertion. 129The medial tendon is interarticular, lying inside the G-H capsule. 39– 41This tendon is not as common a source of shoulder pain as the long tendon, and it rarely ruptures. 39– 41

The function of the biceps as a forearm supinator and secondarily as an elbow flexor is well known. 130At the shoulder joint, however, the function of the LHB tendon is less clear, with most references regarding it as a week flexor of the shoulder. 131Cadaveric studies have suggested that the LHB tendon functions as a humeral head depressor (in full ER), an anterior stabilizer, a posterior stabilizer, a limiter of ER, a lifter of the glenoid labrum, and a humeral head compressor of the shoulder. 132– 135The muscle has also been described as having an important role in decelerating the rapidly moving arm during activities such as forceful overhand throwing. 73In the anatomical position, the biceps has no ability to elevate the humerus. If the arm is rotated 90 degrees externally, the tendon of the long head lines up with the muscle belly to form a straight line across the humeral head. As the biceps contracts in this position, the humeral head rotates beneath the tendon, resisting ER of the humeral head and increasing the anterior stability of the G-H joint. 86, 136, 137Contraction of the LHB in this position fixes the humeral head snugly against the glenoid cavity, as the resultant force passes obliquely through the center of rotation of the humeral head and at right angles to the glenoid. 136The humeral head is prevented from moving upwards by the hood-like action of the biceps tendon ( Fig. 16-7), which exerts a downward force and assists the depressor function of the cuff. 138– 140Interestingly, the biceps tendon was found to be wider in cuff-deficient shoulders in one study. 141

The biceps brachii muscle is innervated by the musculocutaneous nerve.

Biomechanics

The G-H joint has three DOF: flexion/extension, abduction/adduction, and internal/ER. Available ranges of motion at the G-H jointare approximately as follows:

• Flexion and abduction.Approximately 100–120 degrees are available, with females demonstrating slightly more motion than males.
• External rotation.Approximately 60–80 degrees are available, with females demonstrating slightly more motion than males.
• Internal rotation.Approximately 80–90 degrees are available, with females demonstrating slightly more motion than males.
• Extension.Great variability exists with extension, with ranges existing from 10 to 90 degrees.

G-H motions ( Table 16-11) consist of a combination of glides and rolls based on the concave–convex rule (see Chap. 10). At the G-H joint, the concave–convex rule dictates that the articulating surface moves in the opposite direction of the shoulder motion ( Table 16-6). Motions at this joint do not occur in isolation, but rather as coupled motions. 142For example, ER and abduction occur with flexion, and ER and adduction accompany extension. 75

Complete movement at the shoulder girdle involves a complex interaction between the G-H, A-C, S-C, scapulothoracic, upper thoracic, costal, and sternomanubrial joints, the upper thorax, and the lower cervical spine. Within the joints of the shoulder complex, there appear to be no well-defined points within the range where one joint's motion ends and another begins. Rather, they all blend into a smooth harmonious movement during arm raising (see Tables 16-4and 16-5).

During shoulder rotation and arm activities, the scapula invariably acts as a platform upon which the activities are based. It is worth noting that the supporting structures of the G-H joint are only effective if the scapula can maintain its ROM with the humerus (see “The Dynamic Scapula”section).

The G-H joint has been described as being similar to a golf ball on a tee due to the size relationships. A more accurate biomechanical description is that the G-H joint is like a ball on a seal's nose. 143As the ball or humeral socket moves, the seal's nose, or the scapula, needs to move to maintain the position of the ball on the glenoid. The orientation of the G-H joint causes motions at this joint to occur in the scapular plane. The shoulder has the greatest ROM of any joint, with a vast array of muscles producing those motions. 1The correct function of these muscles is dependent on length–tension relationships and coordinated activation. 48Over 1,600 different positions in three-dimensional space can be assumed by the shoulder. 144, 145Due to this wide ROM, the G-H joint is faced with the task of maintaining equilibrium between functional mobility and adequate stability during normal activities of daily living. 146When sport is added to the equation, extremely high forces can be generated at the shoulder. For example, the angular velocity of an overhead throw reaches over 7,000 degrees per second, which is the fastest recorded human movement. 147

The complex kinematics of this region probably account for the fact that strains and sprains may remain symptomatic for much longer than in other joints. 1

Full elevation of the arm occurs through an arc of approximately 180 degrees and can occur in an infinite number of body planes. 149Locally, this motion is a result of abduction of the G-H joint and upward rotation of the scapulothoracic joint. During abduction of the shoulder, the G-H joint is reported to contribute up to 120 degrees of the total arc of motion, with the remaining 60 degrees occurring at the scapulothoracic joint (see “The Dynamic Scapula”section). Arm elevation beyond 90 degrees requires motion in other, more distal joints such as the A-C and S-C joints (see “The Dynamic Scapula”section) and the vertebral joints of the upper thorax and lower cervical spine ( Tables 16-8and 16-9).

Glenohumeral Joint Arthrokinematics

Flexion at the G-H joint involves a pure spin if it occurs strictly in the sagittal plane; no roll or slide is necessary. Tension within the surrounding capsular structures, particularly the posterior structures, may cause a slight anterior translation of the humerus at the extremes of flexion. 46However, although flexion in the sagittal plane involves a pure spin, elevation of the arm in the scapular plane involves a combination of flexion, abduction, and ER. Thus, at the joint surface of the G-H joint during arm elevation in the scapular plane, the head of the humerus spins (flexion component), glides inferiorly (abduction component), and glides anteriorly (ER component) ( Table 16-6).

Functional Movements

Depending on the type of function performed, motions of the shoulder complex involve both local motions and motions at other joints.

Kibler 150labels the motions that occur in other joints of the body during an activity such as throwing (i.e., trunk and hip rotation) as distant functions. In contrast, those motions occurring at the shoulder during the same activity (i.e., G-H ER) are termed local functions.

Distant Functions

The majority of shoulder motions involve a series of sequentially activated links in a kinetic chain of body segments. 145, 150For those motions requiring more force, the number of links in the kinetic chain increases—the sequence of activation starts as a ground reaction force (GRF) and moves up through the knees and hips to the trunk, and into the shoulder. Approximately 50% of the total kinetic energy and force occurring at the G-H joint originate from a combination of the GRF and the forces from the legs and hips. 145, 150, 151At the shoulder, G-H, A-C, S-C, and scapulothoracic joints, motion occurs simultaneously as a result of muscle action and ligamentous tension in these joints. The specific sequence of muscle activation in the upper extremity depends on the activity, although the direction of activation is usually from proximal to distal as this is the most efficient method for producing large forces and accelerations to the arm. As part of this activation sequence, specific muscle activation patterns and joint positions are developed depending on the activity. Any changes to this sequence of activation can produce an abnormal movement pattern, involving substitution or compensation from the more distal links. 47, 152For example, a throwing athlete with decreased trunk rotation due to stiffness has to rely more on the shoulder to provide the force for the throw. These adaptive patterns eventually result in either decreased performance or increased injury risk.

Local Functions

The G-H joint accounts for approximately two-thirds of all shoulder motions, with the remainder provided by the scapulothoracic joint. 87For full motion to occur, a complex interaction between the deltoid, rotator cuff, LHB, G-H capsule, glenoid articulating cartilage, and scapular pivoters (trapezius, serratus anterior, levator scapulae, and rhomboids) is required. 153

Stabilization of the Static Shoulder

The dependent shoulder requires very little muscular support. Its vertical stability is a result of the inferior lateral projection and upward inclination of the glenoid fossa, which is maintained by a mild contraction of the fibers of the trapezius. It was traditionally theorized that the humeral head was prevented from rolling off of this lateral projection by a moderate contraction of the supraspinatus and the deltoid. 134, 154More recent studies have demonstrated that the muscle tone of the rotator cuff is not a significant contributor to the static inferior stability of the dependent shoulder with light loads, but that maintenance of the intra-articular pressure and the adhesion and cohesion properties of the articular surfaces are far more significant. 155, 156However, the rotator cuff does provide a passive restraint to translation, especially to posterior translation, during the early-to-midranges of elevation. 157

During the mid and end ranges of motion, a combination of several different static restraints create a vector that keeps the humeral head securely seated in the glenoid, through concavity compression—negative articular pressure (see Tables 16-7, 16-8, and 16-9). 144, 153, 155, 158– 160Static restraint is also provided by the anatomic curvature of the humerus and glenoid, the extra depth of the labrum, and ligamentous restraints (see Tables 16-7and 16-8). 161The ligamentous restraints contribute especially at the end ranges of motion 162and are assisted with concomitant muscle activity (see Table 16-9).

Stabilization of the Dynamic Shoulder

Dynamic stability of the shoulder complex is dependent on a variety of mechanisms including the optimal alignment of the scapula, correct G-H orientation, and the quality of the length–tension relationship of the involved muscles, and correct functioning of the static restraints ( Table 16-9).

The deltoid, pectoralis major, latissimus dorsi, and teres major muscles are prime movers of the G-H joint. EMG studies have shown that these muscles function along the line of pull, creating the potential for infinite lines of pull that may allow an almost 360 degrees arc of motion. 13, 163Indeed, like the temporomandibular joint, the G-H joint enjoys the benefit that all of its prime movers compress the joint surface, thus optimizing joint stability. The secondary movers of the G-H joint are the LHB, and the triceps.

As motion occurs at the G-H joint, the glenoid cavity of the scapular adopts a diverse number of reciprocal positions. It is likely that these scapular positions are based on both the functional task and the placement of the hand. The scapular stabilizers include the serratus anterior, latissimus dorsi, trapezius, rhomboids, levator scapulae, and the pectoralis minor. Dysfunction or inhibition of any of these muscles can alter the position of the glenoid significantly, resulting in abnormal centering of the humeral head within the glenoid. 24, 164, 165

The function of the rotator cuff in normal and pathologic conditions has been the subject of several studies. 12, 99, 138– 141Until recently, EMG or cadaver studies have been the primary method of evaluating the contribution of each rotator cuff and shoulder muscle to a particular motion or exercise. 12, 99, 138, 142– 145For example, using cadavers, Keating et al. 146determined that the subscapularis contributes 53% of the cuff moment and believed it to be the most important muscle in humeral head stabilization.

Magnetic resonance imaging (MRI) is now being used to show increases in muscle signal intensity detected immediately following exercise. 147– 149On the basis of the level of signal intensity, this so-called exercise-induced enhancement seen on MRI can determine which muscles are used for a given exercise. 140, 147, 148, 150– 152For example, one study of the shoulder 149demonstrated that side-lying abduction produced the greatest signal intensity in the supraspinatus, infraspinatus, and subscapularis muscles. Surprisingly, scaption with internal rotation (SIR), previously associated with isolation of the supraspinatus muscle, did not provide the highest increase in any muscle of the rotator cuff. 149However, caution must be used in drawing conclusions from single studies, and further research is certainly warranted in this area.

As previously mentioned, the role of the capsuloligamentous complex in stabilizing the G-H joint during dynamic activities is complex and varies with both shoulder position and the direction of the translation force. 166The posterior capsule is the main restraint against posterior translation of the humerus on the glenoid fossa with the arm below 90 degrees of abduction. 167With the arm at 90 degrees of abduction, the inferior G-H ligament and the posteroinferior capsule become the main restraint. 167The posterior band of the inferior G-H ligament resists inferior translation when the arm is at 90 degrees of abduction.

The Dynamic Scapula

The synchronized motions that occur between the scapula and the humerus during elevation are a combination of scapulothoracic motion and scapulohumeral motion.

Scapulohumeral Motion

The angle between the glenoid and the moving humeral head has to be maintained within a safe zone of 30 degrees of angulation during activities to decrease shear and translatory forces. 168For this to occur, the scapula must be positioned muscularly in relation to the moving humerus and must also act as a stable base of muscle origin for the rotator cuff muscles. If the scapula cannot be controlled, the glenoid cannot be positioned correctly to allow for the optimal length–tension relationships within the shoulder complex. 110, 112, 161, 169This synchronized motion between the glenoid cavity and the humerus is referred to as scapulohumeral rhythm( Fig. 16-14). Proper rhythm involves a rotation of the scapula during arm elevation. By allowing the glenoid to stay centered under the humeral head, the strong tendency for a downward dislocation of the humerus is resisted and the glenoid is maintained within a physiologically tolerable range ( Fig. 16-14). At full abduction, the glenoid completely supports the humerus.

Several studies have examined the scapulohumeral rhythm three dimensionally. 25, 26, 87, 170, 171An early study by Inman 87determined that a 2:1 ratio existed between the motion occurring at the G-H joint and scapula, respectively. However, more recent studies have shown that this ratio is not consistent throughout the ROM. 21, 107, 153As the humerus elevates to 30 degrees (setting phase), there is minimal movement of the scapula. In this initial portion of abduction, G-H motion predominates and the ratio has been found to be 4.4 degrees of G-H motion for every degree of scapular motion (4.4:1 ratio). From 30 to 90 degrees, the scapula abducts and upwardly rotates, and the ratio becomes 5 degrees of G-H motion to 4 degrees of scapular motion (5:4 ratio). As the shoulder moves above 90 degrees of abduction to full abduction, the scapula abducts and upwardly rotates 1 degree for every 1 degree of humeral elevation (1:1 ratio). 25, 115, 170However, it must be kept in mind that these ratios are based on two-dimensional radiographic projections of angular rotations taken at discrete positions of elevation, whereas in reality, the arm moves in three dimensions, and that the scapulohumeral rhythm has also been found to change with external loading of the arm. 171

Scapulothoracic Motion

Scapulothoracic motion is a vital component of shoulder function and consists of rotation and translation around approximately three axes of motion. These axes are considered to be embedded in the scapula. 172

• Anterior and posterior tipping occurs around an axis parallel to the scapula.
• Protraction and retraction of the scapula occur through protraction and retraction of the clavicle at the S-C joint.
• IR and ER occur around an axis running through the scapula from superior to inferior.

• Elevation and depression of the scapula occurs through elevation and depression of the clavicle at the S-C joint. Throughout the 180 degrees of arm elevation, a total of 30–35 degrees of clavicle elevation occurs, in addition to rotation of the clavicle (30–35 degrees) around its longitudinal axis. 74, 173This clavicular elevation and rotation occur in two main phases of shoulder abduction. Assuming a 2:1 scapulohumeral rhythm, shoulder abduction up to 90 degrees occurs as a summation of 60 degrees of G-H abduction, and 30 degrees of scapulothoracic upward rotation. The 30 degrees of upward rotation occurs predominantly through a synchronous 20–25 degrees of clavicular elevation at the S-C joint and 5–10 degrees of upward rotation at the A-C joint. 103The elevation of the clavicle raises the acromion during arm elevation allowing for the subacromial structures to pass under the coracoacromial arch. 24Shoulder abduction from 90 to 180 degrees occurs as a summation of an additional 60 degrees of G-H joint abduction and an additional 30 degrees of scapulothoracic upward rotation. 103During this late phase, the clavicle elevates only an additional 5 degrees at the S-C joint, whereas, at the A-C joint, the scapula upwardly rotates 20–25 degrees. Thus, by the end of 180 degrees of abduction, the 60 degrees of scapulothoracic upward rotation can be accounted for by 30 degrees of elevation at the S-C joint and 30 degrees of upward rotation at the A-C joint. 103The motion at the A-C joint is controlled by tension in the coracoclavicular ligaments. Finally, the clavicle has been demonstrated in vivo to posteriorly rotate around its long axis during the late phase of shoulder abduction. 24It is, as yet, unclear whether this posterior rotation occurs at the S-C or at the A-C joint. The rotation of the clavicle, though, is controlled by tension in the coracoclavicular ligaments and the clavipectoral fascia.

  Elevation of the arm in the scapular plane in healthy subjects is accompanied by posterior tipping and upward rotation of the scapula. 172The upward rotation of the scapula occurs about an axis that passes through the base of the spine of the scapula and occurs in various phases (see Tables 16-4and 16-5). Rotation of the scapula about the vertical axis shows a somewhat more variable pattern, 172with some studies showing ER occurring predominantly at higher elevation angles, 68, 174, 175whereas others demonstrate IR. 176– 178

• Upward and downward rotation occurs around an axis perpendicular to the plane of the scapula that travels through the A-C joint and S-C joint. 71The upward rotation of the scapula during shoulder abduction helps to maintain an effective length–tension relationship between the three groups (force couples) of muscles that attach to the scapula. A force coupleis defined as two forces that act in opposite directions to rotate a segment around its axis of motion. 86, 179

During the first 30 degrees of upward rotation of the scapula, the serratus anterior muscle and the upper and lower divisions of the trapezius muscle are considered the principal upward rotators of the scapula. Together these muscles form two force couples; one formed by the upper trapezius and the upper serratus anterior muscles ( Fig. 16-14) and the other by the lower trapezius and lower serratus anterior muscles. 6, 87, 180

The prime muscles that abduct the G-H joint are the middle deltoid and the supraspinatus muscles. 103Elevation of the arm through flexion is performed primarily by the anterior deltoid, coracobrachialis, and LHB brachii. 103The trapezius appears to be more critical for controlling the scapula during the initial phases of abduction, whereas the serratus has been found to be the most effective upward rotator of the scapula. 87, 181The lower trapezius contributes during the later phase of shoulder abduction by preventing tipping of the scapula and assisting in the stabilization of the scapula through eccentric control of the scapula during scapular upward rotation. 115, 170

The middle trapezius and rhomboids may also contribute to the scapular motions involved during arm elevation. 182The antagonists are the pectoralis major, teres major, latissimus dorsi, and coracobrachialis, all working eccentrically. Normal motion of the scapula on the thorax is believed to include consistent contact between the thoracic wall, the medial border, and inferior angle of the scapula. 180, 182Loss of this contact has been clinically implicated as evidence of abnormal scapular kinematics. These abnormal scapular kinematics may result in additional stress on the anterior shoulder stabilizers. 183– 185

The appropriate force couples for the acromial elevation that occurs during G-H abduction are the lower trapezius and serratus muscles working together, paired with the upper trapezius and rhomboid muscles ( Fig. 16-14). 24

The EMG activity of the levator scapula muscle, upper and lower trapezius muscles, and serratus anterior muscle during arm elevation increases progressively as the humeral angle increases. 68Activities that maintain an upwardly rotated scapula while accentuating scapular protraction, such as a push-up plus, elicit the greatest serratus anterior EMG activity. 75

The last few degrees of shoulder elevation consist of upper thoracic movement once full G-H joint and shoulder girdle motion have been completed. 186As the arm continues to elevate beyond the 150-degree mark, the thorax begins to extend and ipsilaterally rotate and side flex.

The scapula also functions during retraction and protraction along the thoracic wall (see Fig. 16-11). 24Protraction occurs as the serratus anterior at the scapula and the pectoralis major at the humerus contract simultaneously. Retraction is produced by the combined action of the trapezius and rhomboids. 187A 15–18-cm translation of the scapula around the thoracic wall occurs during retraction and protraction, depending on the size of the individual and the vigorousness of the activity. 24, 151This retraction and protraction is used during activities such as reaching and pulling, respectively. 24

Lastly, the scapula functions to transfer the large forces and energy from the legs, hips, back, and trunk to the actual delivery mechanism, the arm and hand. 24, 150, 188, 189

The intervention strategies for the common pathologies of the shoulder complex are detailed after the examination section. An understanding of both is necessary. As mention of the various pathologies occurs with reference to the examination and vice versa, the reader is encouraged to alternate between the two. Shoulder complex conditions are often multifaceted, and patients with the same shoulder condition often present with diverse physical findings. It is critical that the clinician consider the shoulder girdle as a whole, rather than as a series of isolated articulations, and as a part of the whole kinetic chain. In the presence of shoulder complex dysfunction (assuming systemic or serious causes have been ruled out) there are three likely causes:

• Compromise of the passive restraint components of the shoulder girdle.
• Compromise of the neuromuscular system's production or control of shoulder girdle motion.
• Compromise to one or more of the neighboring joints that contribute to shoulder girdle motion, including
  • the A-C joint,
  • the S-C joint,
  • the joints of the upper thoracic spine and ribs,
  • the joints of the lower cervical spine.

Due to this complexity, all of the above-mentioned joints must be selectively tested in a specific sequence before proceeding with a more detailed examination of the suspected joint or joints.

A good history is the cornerstone of proper diagnosis, especially since shoulder pain has a broad spectrum of patterns and characteristics. A body chart can be used to record the patient's symptom distribution (see Chap. 4). The body chart is a symptomatic representation of a patient's complaints and can be an important element in guiding both the history and the tests and measures.

The history should begin with a brief outline of the patient's profile including age, occupation, hand dominance, recreational pursuits, work requirements, and activities of daily living (ADL). 190Age is occasionally significant 191:

• Children and adolescents may have an epiphysitis of the humerus, or an osteogenic sarcoma.
• Calcific deposits in the shoulder are more common between 20 and 40 years of age.
• Chondrosarcomas usually occur after age 30.
• Rotator cuff degeneration usually occurs in the 40s and 50s.
• A frozen shoulder is more common in those aged 45–60 years and is associated with medical conditions such as diabetes mellitus and ischemic heart disease. 190

The exact mechanism of injury should be determined as it can help with a preliminary diagnosis 192:

• Overhead exertion involving repetitive motions is a common mechanism for subacromial pathology, encompassing subacromial bursitis, 61SIS, 40rotator cuff tendinitis, 40, 193and rotator cuff tear. 194It is also a common cause of bicipital tendinitis.
• A fall on an outstretched hand (“FOOSH” injury) can result in a sprain or strain injury to the wrist, elbow, and shoulder. More serious injuries from such a fall include fractures of the wrist and elbow, A-C separations, clavicular fractures, and G-H fractures and dislocations.
• A fall on the tip of the shoulder is a common mechanism for A-C separation. In addition, this mechanism can result in a compression periostitis (bone contusion) or a cervical spine injury, both of which appear remarkably similar to an A-C separation especially in the early stages.
• Forced horizontal extension of the abducted, externally rotated arm is a common mechanism for anterior dislocation.

It is important to establish the patient's chief presenting complaint (which is not always pain) as well as defining their other symptoms. The most common complaints associated with shoulder pathology include pain, instability, stiffness, deformity, locking, and swelling. 190Patients sometimes complain of catching, clunking, grinding, or popping of the shoulder with various movements. These sounds and sensations may be asymptomatic and nonpathologic. However, they may also indicate pathology including labral disorders, rotator cuff tears, snapping scapular, subacromial bursitis, or biceps tendon disorders, especially if the sound or sensation is associated with pain or instability. 190Periscapular pain is often associated with local muscle strain but may be referred. 1

The quality of the pain is also important. Radicular pain tends to be sharp, burning, and radiating. Bone pain is deep, boring, and localized. Muscle pain can be dull, aching, and hard to localize. Tendon pain tends to be hot and burning. Vascular pain can be diffused, aching, and poorly localized and may be referred to other areas of the body. The intensity of pain may wax and wane with particular motions associated with specific activities. Common complaints with a rotator cuff tear include difficulty with elevation of the arm in abduction, as well as ER, and when patients attempt to put their hand behind their head or back. 195Patients who report difficulty tucking in their shirts may have limited IR from posterior capsular stiffness. 196The hallmark of posterior capsular contracture is symmetric loss of active and passive IR. Posterior capsular stiffness may occur independent of rotator cuff disease. Stiffness or loss of motion at the shoulder may be the chief complaint in conditions such as adhesive capsulitis. 190A-C joint pain tends to occur with arm motion above 90 degrees of abduction and with horizontal abduction. Pain associated with an idiopathic frozen shoulder tends to be constant, but is particularly bad at night and frequently awakens the patient. 53

Weakness may be the chief complaint, leading to some diagnostic confusion. It is important to distinguish true weakness from weakness secondary to pain, both in terms of history and examination findings. 197Painless weakness is usually due to neurological problems or myopathies, although peripheral nerve injuries can be painful ( Table 16-10). Shoulder weakness may be caused by a rotator cuff tear or nerve injury (suprascapular, axillary, long thoracic, or thoracodorsal nerves, or cervical nerve root injury) (see Table 16-10). 111

Symptoms that are not associated with movement should alert the clinician to a more serious condition (see “Systems Review”section). Pain that is worse at night, but increased when rolling onto the shoulder, points to a periarticular mechanical problem. 195

Determining the location of pain is important. Anterior shoulder pain suggests bicipital tendinitis, whereas posterior shoulder pain might be due to a posterior labral tear. 53Posterior neck pain may be indicative of a cervical radiculopathy, as neither the A-C joint nor a subacromial irritation refers pain to this area. 74, 198

Pain due to A-C joint pathology is usually located at the superior region of the shoulder or well localized at the A-C joint itself, and there is often a clear history of injury to this region. Severe pain on top of the shoulder with an associated deformity could indicate an A-C joint sprain.

The clinician should determine which positions or movements relieve the pain, as these can provide helpful information 192:

• Pain relieved with arm elevation overhead could indicate a cervicogenic cause. 200
• Pain relieved with the elbow supported is suggestive of A-C separation and rotator cuff tears.
• Pain relieved by circumduction of the shoulder with an accompanying click or clunk could indicate an internal derangement or subluxation.
• Pain relieved with arm distraction is suggestive of bursitis or rotator cuff tendinitis.
• Pain relieved when the arms are held in a dependent position suggests TOS.

An inquiry about general health, any existing medical conditions, medications, and allergies should be made. Corticosteroid use can cause osteoporosis and tendon atrophy and affects wound healing; therefore a history of its use may alter the differential diagnosis. 190, 195The use of anticoagulantmedication should be noted. Patients who are undergoing renal dialysis are at increased risk for tendon tears, as are patients who are 80 years of age or older. 195Bilateral shoulder involvement is not uncommon in these groups.

Past physical therapy interventions, previous injections, and previous surgery are important to document, as are previous shoulder injuries and what relationship, if any, they have with the present symptomatology. 190

Systems Review

The clinician should be able to determine the suitability of the patient for physical therapy. If the clinician is concerned with any signs or symptoms of a visceral, vascular, neurogenic, psychogenic, spondylogenic, or systemic disorder (see Chap. 5) that is out of the scope of physical therapy, the patient should be referred back to his or her physician or another appropriate healthcare provider.

Scenarios related to the shoulder that may warrant further investigation by the clinician include an insidious onset of symptoms and complaints of numbness or paresthesia in the upper extremity.

The most common causes of numbness in the shoulder and arm are due to cervical or upper thoracic involvement, with either the segmental roots involved or the brachial plexus. The patient should be questioned about recent changes in work requirements or environment, and the presence of neck pain. 39– 41, 201In studies where normal cervical ligaments and muscles, 202cervical zygapophyseal joints, 203and disks 204have been stimulated, subjects have reported pain in the head, anterior and posterior chest wall, shoulder girdle, and upper limb depending on the cervical level stimulated. 115

The Cyriax scanning examination (see Chap. 4) may demonstrate subtle weakness of the cervical root innervated muscles. Depressed or absent upper extremity reflexes are also frequently noted. Finally, reproduction of the patient's pain with cervical motion and not with shoulder movement is a strong indicator of cervical origin.

In addition to the cervical and upper thoracic spine, the related joints referring symptoms to the shoulder require clearing. These include the temporomandibular joint, costosternal joint, costovertebral and costotransverse joint, thoracic spine, and the elbow and forearm. 70, 199

Systemic causes of insidious shoulder pain include rheumatoid arthritis. Rheumatoid arthritis often affects the shoulders and hips in older individuals and can be difficult to distinguish from polymyalgia rheumatica. Morning stiffness lasting for more than 1 hour, constitutional signs, and physical signs of joint inflammation are all indicative of an inflammatory disease. 195Other systemic sources of shoulder pain include lupus erythematosus and gallbladder and liver disease. 70These latter conditions are associated with other signs and symptoms that are not related to movement and are systemic in nature. Chronic respiratory and cardiovascular conditions must also come into consideration. 190The shoulder is very close to the chest and its viscera; therefore reference of symptoms to the shoulder from these structures is common (see Chap. 5). It is vital that questions be asked that would reveal a relationship between the onset of symptoms and local movements versus general exercise, the latter of which could implicate the lung, heart, or diaphragm.

Finally, a vascular examination should be performed and should include an assessment of general skin texture, color, temperature, hair growth, and alteration of sensation about and distal to the shoulder. 53Autonomic signs and symptoms are suggestive of complex regional pain syndrome (CRPS) (refer to Chap. 18). Neurovascular compression or TOS tests are described in “Special Test”section in Chapter 25.

The physical examination of the shoulder complex should be focused and thorough, using the clinical impression gleaned from the history and systems review as a guide.

Observation

Observation of the patient begins when the patient enters the clinic. The clinician observes how the patient holds the arm, the overall position of the upper extremity, and the willingness of the patient to move the arm. During gait, an upper extremity should swing in tandem with its opposite lower extremity. Once in the examination room, the patient is appropriately disrobed and the shoulder is systematically inspected from anterior, lateral, and posterior positions. Total body alignment is examined for overall posture, the relative rotation of the humerus, structural malalignment such as kyphosis, the presence of scars, color changes, and swelling. 190For example, a hollowed infraspinatus fossa is a hallmark of a rotator cuff tear, although a suprascapular nerve lesion should also be considered. 53Anterior prominence of the humeral head or a high-riding outer clavicle suggest G-H dislocation or A-C separation, respectively. 53The relative heights of the shoulder girdles should be assessed. The height of the shoulder may or may not be significant. If the shoulders are elevated, the neck appears short. If they are depressed, the A-C joint is seen to be lower than the S-C joint. 206Elevation of the clavicle can be due to shortness of the upper trapezius such that the lateral end of the clavicle appears appreciably higher than its medial aspect. 206A low shoulder can result from 192

• adaptive laxity of the shoulder,
• leg length discrepancy,
• scoliosis,
• soft-tissue hypertonicity,
• mechanical dysfunction of the pelvis,
• hand dominance —the shoulder on the dominant side may be slightly lower and more muscular than the nondominant side; this is a normal finding.

Deformity is a common complaint with injuries of the A-C joint and fractures of the clavicle. For example, a second-degree sprain or severe first-degree sprain of the A-C joint can be seen as a high-riding lateral clavicle (elevation of the distal end) causing a step-off to form between the clavicle and acromion. 17, 207It is frequently referred to as a tent-pole deformity. The fountain sign describes swelling that is anterior to the A-C joint that is indicative of degeneration that has caused communication between the ACjoint and a swollen subacromial bursa underneath. Other causes of deformity include an anterior dislocation of the shoulder, which may produce a squaring of the shoulder, as the deltoid is no longer rounded out over the humeral head.

Observation of muscle symmetry should be noted. Specific atrophy can imply certain diagnoses. For example, muscle weakness or atrophy, especially posttraumatic, might indicate peripheral nerve damage 208:

• Atrophy of the deltoid from axillary nerve neuropathy can result in a squared appearance of the lateral shoulder, 207, 208which is best observed from the front. 17
• Atrophy of the posterior deltoid can occur in patients with multidirectional instability. 208
• Atrophy at the infraspinatus or supraspinatus fossa is a hallmark of a rotator cuff tear 16or suprascapular nerve entrapment. Wasting of the supraspinati and infraspinati can be determined by pushing the examining finger into the respective muscle bellies.
• Atrophy of the trapezius may indicate compromise of the spinal accessory nerve. Atrophy of the trapezius is characterized by the appearance of a shoulder girdle that droops in association with a protracted inferior border of the scapula and an elevated acromion. 24, 110, 209
• Atrophy of the serratus anterior muscle can create a prominent superior medial border of the scapula and a depressed acromion.

A balled-up muscle may indicate a muscle rupture, the most common of which are of the biceps and infraspinatus. Rupture of the LHB can be noticed by the change in contour of the anterior arm with bunching of the muscle (the “Popeye” appearance). 190

Observable swelling in the shoulder may indicate a serious problem or damage.

The position and attitude of the scapula, both statically and dynamically, should be noted (see later). In standing, with their arms by the sides, the patients' medial (vertebral) border of the scapula should be 5–8 cm lateral to the thoracic spinous processes, 191, 210the medial end of the spine of the scapula should be level with the T3 spinous process, and the inferior angle of the scapula should be level with the T7 spinous process. The superior aspect of the medial border of the scapula begins at the level of the spinous process of T2 and extends to the level of the spinous process of T7. Excessive prominence of the scapular spine may indicate atrophy of the infraspinatus and supraspinatus. 208Two conditions, which may present with deformity of the scapula as their main symptom, are Sprengel's deformity and winging of the scapula. 190

Sprengel's deformity is the most common congenital abnormality affecting the shoulder. It is characterized by the presence of a hypoplastic, incorrectly rotated scapula, which sits abnormally high on the posterior chest wall. The condition results from a failure of the normal descent of the scapula, which occurs in utero, and is commonly associated with other significant musculoskeletal and visceral congenital abnormalities. 190

Winging of the scapula ( Fig. 16-15) is due to a loss of the normal scapular stability. Subtle forms of scapular winging, usually evident at the inferior border, occur commonly with many shoulder disorders such as G-H joint stiffness and shoulder instability. 112In cases of G-H joint stiffness, there is passive limitation of G-H motion, while with instability there is evidence of excessive movements or positive apprehension signs. Scapular winging may occur as the result of serratus anterior weakness, trapezius palsy, 209excessive shortening of the pectoralis minor muscle, 2or myopathies. 190, 211– 213Scapular winging may also be caused by G-H joint stiffness, shoulder instability, and rotator cuff disease (see “Analysis of the Static Scapula”section).

Gait

Gait is evaluated to observe freedom of the arm swing, reciprocal upper extremity movement, position of the arms and scapulae, and motion of the trunk and lower extremities (see Chap. 6). 70, 199

Posture

An analysis of posture prompts the clinician as to the area of movement disturbance or excessive stresses. Postural dysfunctions of the upper quarter are a common cause of shoulder pain. A wide variety of structural changes can produce shoulder pain. 183, 214, 215Poor positioning of the cervical or thoracic spine may alter the position of the shoulder girdle. 216, 217For example, thoracic kyphosis, scoliosis, or neck lordosis can result in excessive protraction of the scapula, producing interscapular pain. 24, 218In the older patient (aged over 50 years), an increased thoracic kyphosis may be related to a decrease in shoulder elevation. 219

The relationship of the humeral head to the acromion should be observed. One-third of the humeral head should be anterior to the acromion. A finding of less than one-third may indicate a tight posterior capsule or adaptive shortening of the external rotators. 220

The patient's hands and arms should also be observed. Normally, the thumb faces anterior or slightly medial. If the posterior aspect of the hand faces anteriorly, there may be excessive adaptive shortening of the internal rotators. 220

Muscle balances in the upper quadrant can cause a characteristic postural pattern of the forward head position. 221The most common muscle imbalances are outlined in Table 16-11. The clinician should observe the trunk and neck positions in sitting and standing, as well as the relationship of the scapulae relative to the trunk and the humerus relative to the acromion. Any change in the scapular position has an impact on the A-C and S-C joint and can also alter the length–tension relationship of the scapular muscles.

The forward head and rounded shoulder posture include an abducted and elevated position of the scapula and an internally rotated humerus, 24, 102, 217, 222and is more common in patients presenting with shoulder pain 223and interscapular pain. 223Forward head posture (FHP) in the presence of abducted scapulae and protracted shoulders results in a decrease in the size of the subacromial space, which may predispose the patient to rotator cuff disorders. 224This posture results in an adaptive shortening of the upper trapezius, levator scapulae, and pectoralis, with weakening and lengthening of the deep neck flexors and lower scapular stabilizers. 102, 223, 225

If the pectoralis major is tight or strong, the muscle will be prominent. If there is an imbalance present, it will lead to rounded and protracted shoulders and a slight IR of the humerus. 226, 227The altered position of the scapulae can distort the course of the suprascapular nerve, placing it at risk for a traction injury during upper extremity movements. 228– 230

Normally, the insertion of the SCM is barely visible. If the clavicular insertion is prominent, it may indicate adaptive shortening of the SCM. 226A groove along the SCM is an early sign of weakness of the deep neck flexors. A weakening and atrophy of the deep neck flexors has been proposed as a sign to estimate biological age. 231The change in the anatomical relationship of the clavicle associated with this weakness and atrophy, decreases the width of the thoracic inlet, rendering the brachial plexus vulnerable to compression (refer to Chap. 25). 228, 232, 233

A loss of bulk in the interscapular muscles may indicate tightness in the trapezius and levator scapula.

Analysis of the Static Scapula

An abnormal position of the scapula at rest is common in patients with shoulder overuse injuries. 102, 206, 223, 225The scapular position is initially examined with the arms by the side. The clinician notes any signs of winging, elevation, depression, adduction, abduction, and rotation of the scapula. Abnormalities in alignment include a flattening of the interscapular area and an increase in the distance between the thoracic spinous processes and the medial border of the scapula. When the scapula is abducted (more than 8 cm from the midline of the thorax), it is also rotated more than 30 degrees anterior to the frontal plane and produces a medial rotation of the humerus. 206

Tipping of the scapula, in which the inferior angle protrudes away from the rib cage, often results from a weakness of the lower trapezius and positions the glenoid fossa so that it faces a more inferior direction. 115This alignment is often associated with shortness of the pectoralis minor muscle or biceps brachii muscle. 206

Adaptive shortening of the rhomboids and levator scapulae muscles, in the presence of a lengthened upper trapezius and serratus anterior, results in an elevation of the scapulae at the superior angle, and a downward rotation of the scapula. This causes the G-H joint to move into a position of abduction. 206, 234In addition, if the levator scapula adaptively shortens, both cervical and shoulder motions occur sooner than normal because the starting position of the scapula is changed. This modification to the starting position of the scapula for shoulder-elevated tasks presumably has an effect on the timing of the scapular muscles responsible for upward rotation. This results in an end position of arm elevation that is lower than usual (see “Examination of the Dynamic Scapula”section). 115

Extremity dominance can affect the orientation of the scapula, with the greater degree of unilateral activity producing the greater changes. A bilateral comparison should be made and allowances made for the dominance. Bilateral comparisons do not always highlight dysfunctions. For example, the symmetrical effects of an adaptive shortening of the anterior chest and shoulder musculature, and lengthening of the posterior musculature that occurs in the forward head and rounded shoulder posture, will not be confirmed until during the mobility tests.

A number of static tests for the scapular position exist. The amount of scapular protraction available can be measured clinically using the method described by Diveta et al., 235who advocate two linear measurements with a piece of string. The distance in centimeters between the root of the scapular spine and the inferior angle of the acromion (scapular width) is divided into the distance from the third thoracic spinous process to the inferior angle of the acromion (scapular protraction). The resulting ratio provides a measurement of scapular protraction corrected for scapular size (normalized scapular protraction). This method of measurement of scapular protraction has been found to be both reliable and valid when compared with radiographic measurements. 223, 235, 236

Palpation

Palpation must be performed in a systematic manner and must focus on specific anatomical structures (refer to Figs. 16-1, 16-2, 16-3, 16-4, 16-5, 16-6, 16-7, 16-8, 16-9, 16-10, 16-11, 16-12, and 16-13). The degree and location of tenderness is often a reliable physical sign leading to an accurate diagnosis. 53For example, tenderness over the anterior acromion and greater tuberosity is suggestive of impingement, whereas tenderness over the posterior joint line could indicate joint pathology such as G-H arthritis or a torn posterior labrum. 53Traditionally, palpation has been viewed as a static process. However, palpation is a dynamic process and should be performed along with other aspects of the examination. The optimal methods of palpating the shoulder tendons occur in regions where there is the least amount of overlying soft tissue. 237

It is best to divide the shoulder complex into compartments for palpation as symptoms reproduced by palpation in these compartments are frequently associated with a specific underlying pathology.

Anterior and Superior Compartment

The clinician should begin anteriorly, with palpation of the contours of the clavicle. The anterior and superior aspects of the clavicle are covered by the platysma muscle. The sternal end of the clavicle, which projects cranially over the border of the manubrium, is covered by the SCM. The following areas related to the clavicle should be palpated for tenderness, swelling, or symptom reproduction:

• The supraclavicular fossa, bordered medially by the SCM and laterally by the omohyoid.
• The infraclavicular fossa, between the pectoralis major, deltoid, and clavicle. The coracoid process is located in the infraclavicular fossa, especially if the arm is placed in extension. Several palpable ligaments and muscles attach here including the coracoclavicular, on the conoid tubercle, the coracoacromial ligament, the pectoralis minor, the coracobrachialis, and the short head of the biceps. A prominent coracoid could indicate a posterior dislocation of the shoulder.
• The subclavius and costoclavicular ligament.
• The suprasternal (jugular) notch—this indentation on the superior border of the sternal manubrium is an important reference point. Three centimeters above the notch is the inferior border of the larynx, while the sternal bellies of the SCM form the sides of the notch. The interclavicular ligament is located within the notch. Disruption of the normal contours of the notch is associated with S-C dislocations.
• The S-C joint and joint line—arthrotic changes of the S-C joint are evidenced by crepitus at the joint during IR/ER of the humerus with the arm abducted to 90 degrees. The contours of the S-C joint are palpated and a comparison should be made with the contralateral side. Thickening of the S-C, or an S-C dislocation, produces an inability to abduct the arm.
• The A-C joint—injuries and arthritis of this joint are common, and focal tenderness is an important sign of A-C pathology. 190Changes in the size and shape of the joint may indicate past or present separation, fracture, or osteoarthritis.

With the arm hanging by the side and the palm facing the body, the greater tuberosity lies laterally, and the lesser tuberosity lies anteriorly with respect to each other. They are separated by a bicipital groove. The bicipital groove is made more accessible for palpation with IR of the arm to 15–20 degrees. 237, 238Within this groove lies the biceps tendon, which should be palpated for tenderness. If the arm at rest appears slightly abducted and externally rotated, an anterior dislocation might be present. An adducted and internally rotated arm suggests many shoulder conditions, including a posterior dislocation.

The lesser tuberosity (shaped like an inverted teardrop) is palpated during passive IR and ER of the humerus at a point lateral to the coracoid process. The subscapularis can be palpated deep in the deltopectoral triangle at its insertion into the lesser tuberosity. This is accomplished by positioning the arm by the side in neutral rotation, and palpating just lateral to the coracoid. 237

The greater tuberosity is located directly anterior to the acromion. It is best located with the patient in side-lying, facing the clinician, with the upper arm in front in approximately 60 degrees of shoulder flexion. The clinician palpates laterally along the spine of the scapula until contact is made with the superior facet of the greater tuberosity. The supraspinatus and posterior coracohumeral ligament insert into the superior facet, the infraspinatus on its middle facet, and the teres minor on its inferior facet. The supraspinatus, located just distal to the anterolateral corner of the acromion, can be made more discernible by positioning the patient's arm behind the back in slight extension. 237, 239

The subacromial–subdeltoid bursa can be palpated by putting the the patient in the prone position, and passively stretching the arm into extension before palpating anterior to the A-C joint. Tenderness reported with shoulder extension and relieved with shoulder flexion is indicative of an inflammation of this bursa.

The anterior joint capsule can be located by palpating one fingerbreadth lateral to the coracoid process with the arm by the side. Persistent tenderness at this point with IR and ER of the arm suggests capsular involvement. 240

The muscle bellies, origins, and insertions of the upper trapezius, supraspinatus, and levator scapula should be palpated for tenderness or asymmetries.

Lateral Compartment

The deltoid muscle belly and insertion should be palpated for tenderness or atrophy.

Posterior Compartment

The spine of the scapula should be located. The clinician should be able to locate the inferior pole of the scapula, the medial border of the scapula, and the posterior angle of the acromion. The superior angle of the scapula should be level with the second rib, the spine of the scapula with the level of T3, and the inferior border with the level of T7.

The infraspinatus can be palpated just distal to the posterolateral acromion with the arm at 90-degree flexion and 10-degree adduction. 237The teres minor is isolated and palpated using the same patient position. 237To help locate the teres minor, the long head of the triceps is palpated by placing the patient's arm at 90 degrees of abduction followed by extension. Once the long head of the triceps is located, the patient is repositioned and the teres minor, now superior to the long head of the triceps, can be palpated. Tenderness of the posterior capsule suggests capsular laxity.

Inferior Compartment

The lymph nodes in the axilla are palpated for swelling or tenderness. Also located in the inferior compartment are the anterior coracohumeral ligament, G-H ligament, transverse humeral ligament, and pectoralis major. The latissimus dorsi tendon can be palpated deep in the axilla.

The teres major tendon is palpated medial to the supeior part of the latissimus dorsi tendon insertion. It can be differentiated from the latissimus dorsi by using a combination of isometric IR and adduction with the patient's shoulder positioned at 90 degrees of abduction and maximum ER.

The subscapularis tendon is palpable between the serratus anterior and the latissimus dorsi while the patient's arm is elevated.

Active and Passive Range of Motion

Due to the complex nature of the arthrokinematics, osteokinematics, and myokinetics of this region, the results from the active and passive movements can be misleading; therefore care must be taken with interpretation of the findings. Passive testing should be performed when active motion is incomplete. Pain with end-range stress is an important clinical finding. Crepitus can be soft with rotator cuff pathology or harsh with G-H arthritis. Active motion testing provides the clinician with information regarding the following:

• Overall functional capacity of the shoulder.
• Painful or hesitant initiation or termination of movement. Such a hesitation may be a subtle sign of instability or rotator cuff dysfunction. 241
• Quantity of movement ( Table 16-12). Estimation of true G-H motion is performed by fixing the scapula at its inferior border.
• Developed trick movements or modifications to the movement, such as an altered plane, the use of trunk movements, or abnormal recruitment of muscles.
• Associated signs and symptoms not reproduced with nonfunctional motion testing.
• Presence of a capsular pattern ( Table 16-13).
• Detection of a “painful arc.”
• End-feels (see Table 16-12), if passive overpressure is applied.

McClure and Flowers 242classify limited shoulder motion into two categories:

• Decreased ROM secondary to changes in the periarticular structures, including shortening of the capsule, ligaments, or muscles, as well as adhesion formation. Clinical findings for this category include a history of trauma, 243– 245immobilization, 243– 245presence of a capsular pattern, 246capsular end-feel, 246and no pain with the isometric testing. 246
• Decreased ROM due to nonstructural problems, including the presence of pain, protective muscle spasm, or a loose body within the joint space. 247Clinical findings for this patient include a history of trauma or overuse, and the presence of a noncapsular pattern of motion restriction.

Riddle et al. 248examined the intratester and intertester reliabilities for clinical goniometric measurements of shoulder passive ROM (PROM) using two different sizes of universal goniometers. Patients were measured without controlling therapist goniometric placement technique or patient position during measurements. Repeated PROM measurements of shoulder flexions , extension , abduction , shoulder horizontal abduction, horizontal adduction, external rotation , and internal rotation were taken for two groups of 50 subjects each. The intratester intraclass correlation coefficients (ICCs) for all motions ranged from 0.87 to 0.99. The ICCs for the intertester reliability of PROM measurements of horizontal abduction, horizontal adduction, extension, and internal rotation ranged from 0.26 to 0.55. The intertester ICCs for PROM measurements of flexion, abduction, and external rotation ranged from 0.84 to 0.90. Goniometric PROM measurements for the shoulder appear to be highly reliable when taken by the same physical therapist, regardless of the size of the goniometer used.

The patient is asked to bring the arm actively through the ranges of motion. These motions include flexion, extension, abduction, IR ( Fig. 16-43), ER, horizontal adduction, and shrugging of the shoulders.

Arm Elevation

The clinician should view the patient carefully as he or she attempts arm elevation. Elevation in the frontal plane ( Fig. 16-16) and scapular plane is assessed. Typically, 170–180 degrees of elevation is possible in both of these planes, with the upper portion of the arm being able to be placed adjacent to the head. If the patient is unable to achieve 170–180 degrees, the clinician must determine where and why movement is not occurring. The presence of pain with arm elevation can provide the clinician with valuable information ( Fig. 16-17). A common cause of pain with arm elevation is rotator cuff tendinopathy. If there is an arc of pain, the point in the range where the arc of pain occurs can be diagnostic in implicating the cause.

• Pain that occurs between 70 and 110 degrees of abduction is deemed a “painful arc” and may indicate rotator cuff impingement, or tearing, or subacromial bursitis. 76
• Pain which occurs in the 120–160/160–180-degree range may indicate involvement of the A-C joint. 76

Kibler 24advocates the use of the “muscle assistance” or “scapular assistance” test (SAT) to assess scapular motion and position during elevation and lowering of the arm to see if the impingement may be due to a lack of acromial elevation ( Fig. 16-18). As the patient elevates the arm, the clinician pushes laterally and superiorly on the inferior medial border of the scapula to simulate the serratus anterior/lower trapezius force couple. The test is considered positive if the manual assistance diminishes or abolishes the impingement symptoms. 24The SAT is presumed to indirectly measure the function of the scapula rotators; however, other factors, such as thoracic posture and pectoralis minor length, have also been hypothesized to affect scapular rotation, and it is possible that these could be affected by the manual pressure provided during the SAT. 172, 249, 250More importantly, the SAT is used to directly assess the influence of scapular motion on shoulder pain. In a study by Rabin et al., 172a modified version of the SAT, which included assisting posterior tipping of the scapula in addition to assisting upward rotation of the scapula, was found to possess acceptable interrater reliability for clinical use to assess the contribution of scapular motion to shoulder pain. The κcoefficient and percent agreement were 0.53 and 77%, respectively, when the test was performed in the scapular plane, and 0.62 and 91%, respectively, when the test was performed in the sagittal plane. In the modified version, the clinician places one hand on the superior aspect of the involved scapula, with the fingers over the clavicle. The other hand is placed over the inferior angle of the scapular so that the heel of the hand is just over the inferior angle and the fingers are wrapped around the lateral aspect of the thorax. The patient is asked to actively elevate his or her arm in the scapular plane, and during the movement the clinician facilitates upward rotation of the scapula by pushing upward and laterally on the inferior angle, as well as tilting the scapula posteriorly by pulling backwards on the superior aspect of the scapula.

Weakness of the serratus anterior muscle, due to palsy or disuse, produces winging of the scapula as the patient attempts to elevate the arm. 4, 111, 113In addition to winging, serratus anterior dysfunction presents with loss of scapular protraction during attempted shoulder elevation and the inferior tip of the scapula becomes prominent. 110

Abduction of the shoulder requires a greater use of the upper and lower trapezius muscles, whereas shoulder flexion is more likely to recruit the serratus anterior muscle. 87, 181

Although lesions to the deltoid are rare, imbalances of the deltoid and the rotator cuff are common. When the deltoid becomes dominant, the humeral head is seen to glide superiorly during arm elevation because the downward pull of the rotator cuff muscles is insufficient to counterbalance the upward pull of the deltoid ( humeral superior glide syndrome). 206This alteration in the G-H force couple usually occurs during the middle phase of elevation 170(between 80 and 140 degrees), because the upward translation force of the deltoid peaks during this phase, requiring more compressive and depressive forces from the rotator cuff muscles. 251, 252

An anterior glide of the humeral head, which occurs during arm elevation ( humeral anterior glide syndrome) 206suggests that the posterior deltoid has become the dominant external rotator. 206This syndrome should be suspected if the pain is located in the anterior or anterior medial aspect of the shoulder and is increased by G-H IR, shoulder hyperextension, and horizontal abduction, and is decreased when the humeral head is prevented from moving anteriorly during shoulder rotation and flexion movements. 206

When compared, the range achieved for unilateral elevation should be greater than that achieved when bilateral arm elevation is attempted. This is because the joints of the cervicothoracic junction have to be permitted to rotate toward the elevating arm. The clinician should observe the smoothness of the scapulohumeral rhythm during elevation and the ratio between the scapular upward rotation and G-H elevation (see “Examination of the Dynamic Scapula”section).

Compressive forces across the A-C joint occur mainly in the terminal 60 degrees of abduction. This often causes pain during this range if pathology exists at this joint. 190

Extension

Active extension ( Fig. 16-19) is normally 50–60 degrees. Care must be taken when measuring this motion as substitutions can occur to seemingly increase extension by bending forward at the waist or by retracting the scapula. Asymmetry of shoulder extension can indicate weakness of the posterior deltoid in one arm (swallowtail sign).

Rotation

The following arm positions can be used to assess IR and ER:

• The arm at shoulder level (at 90 degrees of shoulder abduction, 90 degrees of elbow flexion and with the palm parallel to the floor). Normal ER ( Fig. 16-20), which is performed by rotating the hand toward the floor, is 90 degrees or beyond. Assessing ER in this position is helpful in determining the presence of a fracture of the greater tuberosity, or a decrement in the performance of a throwing athlete. IR is then carried out ( Fig. 16-21), rotating the hand toward the hip, as if positioning it behind the body. Normal IR approaches 90 degrees. However, this test position is often uncomfortable and not very functional, except for pitchers.
• The arm to the side and the elbow flexed to 90 degrees. ER is performed by moving the hand away from midline ( Fig. 16-22), and IR is performed by moving the hand toward the abdomen ( Fig. 16-23). Again, it is important to assess active and passive range, because a loss of active motion alone may indicate muscular weakness.
• The arm at the side and the forearm behind the back (Apley scratch test). This measurement for IR is assessed by the position reached with the extended thumb up the posterior (dorsal) aspect of the spine using the spinous processes as landmarks ( Fig. 16-24). 253This is more of a functional test, and the thumb tip of normal subjects will reach the T5–T10 level. 190Loss of motion with this test affects the patient's ability to perform toileting duties, hook bras behind the back, reach into a back pocket, and tuck in shirts. 254The examination is made relative to the opposite side, as there is quite a large variation in range among normal subjects. In a study by Hoving et al., 255which assessed the intrarater and interrater reliability among rheumatologists of a standardized protocol for measurement of shoulder movements, the movement of the hand behind the back (and total shoulder flexion) yielded the highest ICC scores for both intrarater reliability (0.91 and 0.83, respectively) and interrater reliability (0.80 and 0.72, respectively). However, in a study by Edwards et al., 256measurement of IR by vertebral level was not readily reproducible between observers.
• The arm at 45-degree abduction in the scapular plane ( Fig. 16-25). This position is used to assess ER for overhead athletes.

Most overhead athletes exhibit excessive ER and decreased IR. The cause of this adaptation has not been established, with some authors 257– 260documenting humeral osseous retroversion as the cause, whereas others have theorized that excessive ER and limited IR are due to anterior capsular laxity and posterior capsule tightness, 261although no clinical studies have confirmed these findings to date. G-H IR deficit (GIRD) and posterior shoulder tightness (PST) have been linked to shoulder dysfunction based on a study series by Burkhart et al. 261– 263In cadaveric studies, tightening the posterior capsule by plication has been shown to increase anterior G-H translation during flexion and cross-body adduction, cause superior G-H translation with flexion and ER of the G-H joint, and markedly decrease IR. 46, 264, 265Similarly, GIRD and PST have been demonstrated in throwing athletes with internal impingement 266and in patients with secondary impingement. 267However, the theory of posterior capsule tightness has come into question from other researchers who have determined that ROM in baseball pitchers—specifically, a loss of IR—does not correlate with an alteration in posterior G-H translation. 268, 269

It is important not to disregard the effect of muscle forces on these biomechanical changes. Reinold et al. 270recently examined the PROM of the shoulder in 31 professional baseball pitchers, before and immediately after pitching. The researchers reported that rotational range of G-H motion was immediately affected by overhead throwing and that mean IR ROM after pitching significantly decreased (73 ± 16 degrees before, 65 ± 11 degrees after) and total rotational motion decreased (average, 9 degrees). Mean ER before throwing (133 ± 11 degrees) did not significantly change after throwing (131 ± 10 degrees). The researchers hypothesized that this decrease in IR ROM was due to large eccentric forces being generated in the external rotators during the follow-through phase of throwing that caused microscopic muscle damage in the posterior shoulder musculature. Previous studies examining the effect of repetitive eccentric contractions have shown a subsequent loss of joint ROM in the upper and lower extremities following testing. 271– 273

Wilk et al. 274proposed the TRM concept, where the amount of ER and IR at 90 degrees of abduction are added and a TRM arc is determined. The authors reported that the TRM in the throwing shoulders of professional baseball pitchers is within 5 degrees of the nonthrowing shoulder 274and that a TRM arc outside the 5-degree range may be a contributing factor to shoulder injuries and subsequent surgery. 275Thus, although the dominant shoulder has greater ER and less IR, the combined total motion should be equal bilaterally. 270

Horizontal Adduction

Horizontal adduction is performed by bringing the arm across in front of the body ( Fig. 16-26). Pain with horizontal adduction may indicate A-C joint pathology (see “Crossover Impingement/Horizontal Adduction Test”section). Horizontal adduction is normally 130 degrees compared with 50–75 degrees if the arm is brought in front of the body.

The patient then completes the motions of shoulder girdle elevation (shrug) and depression and shoulder protraction and retraction. An inability to shrug the shoulder may indicate a trapezius palsy. 110Hiking of the shoulder and the scapular during arm elevation is often seen in patients with large rotator cuff tears. 195

Movement combinations are assessed.

PROM is performed if there is a deficiency in active motion to determine the end-feel. 246Traditionally, PROM has been performed with the patient positioned in supine Given the importance of scapular motion during humeral elevation, care must be taken to not prevent the scapula from rotating during these tests.

A discrepancy between active and passive motion may indicate a painful periarticular condition. 227Loss of active motion with preservation of passive motion is likely caused by a rotator cuff tear, 61or rarely, suprascapular nerve injury. 201, 276A severely restricted active abduction pattern with no pain is suggestive of a rupture of the supraspinatus or deltoid. Loss of both active and passive motion is usually caused by adhesive capsulitis. 205

A loss of PROM or active ROM (AROM) may be associated with a loss of flexibility in the passive restraints to motion. This can occur with both single plane motions and combined motions. 37, 277– 280For example, if both IR and ER are restricted and muscle tightness has been ruled out as a cause, an adhesion of the middle G-H ligament is implicated. 280

Examination of the Dynamic Scapula

Given the importance of the scapulothoracic joint to overall shoulder function, it is important to examine the scapulothoracic joint arthrokinematics and muscle power. 281

A number of muscles play an important role in the kinematics of the scapula, including the trapezius and serratus anterior. Increased activity of the upper trapezius muscle, or imbalances between the upper and the lower trapezius muscle, during shoulder elevation may have adverse effects on the kinematics of the scapula. 93, 115, 183, 282

According to Sahrmann, 206four abnormal clinical findings exist for the scapula:

• The scapular alignment is correct but its movement is impaired.
• The scapular alignment is impaired and its movement is impaired.
• The scapular alignment is impaired and its movement is of normal range, but does not correct or compensate for the impaired start position.
• The scapular alignment is impaired but its movement is sufficient to compensate for the impaired start position.

Kibler 24recommends the use of the isometric “scapular pinch” test to examine the strength of the medial scapular muscles. This involves the patient squeezing his or her shoulder blades together ( Fig. 16-27). Normally, the scapula can be held in this position for 15–20 seconds without difficulty. If a burning pain occurs in less than 15 seconds, Kibler suggests that scapular muscle weakness may be the cause. 24

Observation of the scapulohumeral rhythm and scapulothoracic motion should reveal that the scapula stops its rotation when the arm has been elevated to approximately 140 degrees. Upon completion of the elevation, the inferior angle of the scapula should be in close proximity to the midline of the thorax, and the vertebral border of the scapular should be rotated 60 degrees. Movement beyond these points may indicate excessive scapular abduction. 206At the end range of elevation, the scapula should slightly depress, posteriorly tilt, and adduct. 206The motion of the scapula should be assessed carefully in patients with suspected multidirectional instability. A scapulothoracic dyskinesia (decrease in scapular abduction and ER with progressive arm abduction) is often observed in patients with anteroinferior instability. 283Posteroinferior instability is characterized by excessive scapular retraction. 238An inferior instability is characterized by a drooping of the lateral scapula or “scapular dumping.” 238

After positioning the patient in prone with his or her arm abducted to 90 degrees, ER is carried out to test the ability of the scapula to remain in its correct position rather than abducting due to excessive lengthening of the thoracoscapular muscles (trapezius and rhomboids) and shortening of the scapulohumeral muscles. 206

Resistive Tests

In addition to pain, shoulder dysfunction is often caused or exacerbated by a loss of motion or weakness. The resistive tests assess function in the important muscle groups of the upper kinetic chain ( Tables 16-14and 16-15).

Localized, individual isometric muscle tests around the shoulder girdle can give the clinician information about patterns of pain and weakness and with information regarding weakness resulting from a spinal nerve root or peripheral nerve palsy. A general assessment of shoulder strength is initially performed, testing flexion, extension, abduction, adduction, IR, and ER. Weakness on isometric testing needs to be analyzed for the type—increasing weakness with repeated contractions of the same resistance indicating a palsy versus consistent weakness with repeated contractions, which could suggest a deconditioned muscle or a significant muscle tear—and the pattern (spinal nerve root, nerve trunk, or peripheral nerve). A painful weakness (see Chap. 5) is invariably a sign of serious pathology and, depending on the pattern, could indicate a fracture or a tumor. However, if a single motion is painfully weak, this could indicate muscle inhibition due to pain. The various motions of shoulder can be assessed through their arcs of motion both concentrically and eccentrically against resistance, as appropriate.

A number of resistive tests have been designed to isolate the muscles of the shoulder complex. Cyriax 275believed that supraspinatus tendinitis is the most common cause of a painful arc. The supraspinatus can be tested using the Jobe test or empty-can position ( Fig. 16-28) . The patient's arm is positioned in IR within the scaption plane, at approximately 90 degrees of shoulder flexion. Manual resistance is then applied by the clinician in a direction toward the floor. The Jobe test can be performed similarly with the humerus externally rotated (full-can test) ( Fig. 16-29) . One study 284found the empty-can test to have a high sensitivity of 86% and a low specificity of 50% in diagnosing supraspinatus tendon tears in a series of 55 patients. However, in another study, 285the full-can test had higher specificity (74% vs. 68%) and an equal sensitivity of 77% when compared with the empty-can test in a series of 136 patients.

A partial rupture of the supraspinatus tendon will result in abduction that is both weak and painful. 69A painless weakness with abduction could indicate a complete rupture of the supraspinatus tendon, although the deltoid cannot be ruled out. The tendon of the supraspinatus can be passively stretched by positioning it in adduction and IR to see if this increases the pain. 286

It has been documented that if coracohumeral pain decreases with the addition of arm traction during resisted abduction, subacromial–subdeltoid bursitis or an A-C joint lesion should be suspected. 287However, this was not found to be the case with ultrasonography. 288

The test position for the infraspinatusand teres minormuscles is 90 degrees of G-H flexion and one-half full ER ( Fig. 16-30). 120If the pain is isolated to ER, then the infraspinatus is at fault. If ER and resisted adduction are painful, the teres minor is at fault, although isolated involvement of the teres minor is not common. To test the teres minor further, the muscle is placed on stretch by putting the patient in prone position with his or her upper arms vertical, adducted, and externally rotated to approximately 20 degrees. The patient is asked to lean toward the tested side to increase the adduction.

The teres majormuscle can be tested by putting the patient in the prone position with his or her hand resting on his or her lower back ( Fig. 16-31) . The patient is asked to adduct and extend the humerus while the clinician applies resistance at the elbow into shoulder abduction.

To assess for rhomboiddominance, the patient positions their arms by their side with their elbow flexed to approximately 90 degrees. Resisted ER in this position should not result in any scapular adduction, unless there is rhomboid dominance and poor control of G-H ER. 206There should also be no superior or anterior gliding of the humerus during this test, unless deltoid dominance is occurring. 206

Conditions to be ruled out if there is a painless weakness of ER include, but are not limited to, the following:

• A complete rupture of the infraspinatus tendon
• A C5 nerve root palsy
• A suprascapular nerve palsy
• Neuralgic amyotrophy

The subscapularisis best assessed using the lift-off test as described by Gerber and Krushell. The lift-off test is performed with the arm internally rotated so that the posterior surface of the hand rests on the lower back. Actively lifting the hand away from the back ( Fig. 16-32) against a resisting force suggest integrity of the subscapularis. Failure to do so indicates a subscapularis tear. The test has been found to have a sensitivity of 80% and a specificity of 100% for a tear of the subscapularis. 291A similar test is the IR lag sign test (see “Special Tests”section).

Resisted adduction is tested with the arm at 0 degree of abduction so that the subscapularis is not facilitated. 291Pain with resisted adduction tends to be fairly rare, but could implicate the pectoralis major, latissimus dorsi, teres major, and teres minor.

Testing of deltoidfunction is best done with resisted abduction with the arm at 90 degrees of abduction and neutral rotation ( Fig. 16-33) . 190A painful arc cannot be produced by a lesion to the deltoid muscle due to its anatomical position.

Differential diagnosis will be needed to rule out several neurological disorders, which may provoke painless weakness on resisted abduction. These include an axillary nerve palsy, a suprascapular nerve palsy, or a fifth cervical root palsy.

The three components of the trapeziusare assessed as follows:

• Upper trapezius (and levator scapulae).Usually both sides are tested simultaneously. The patient is asked to shrug the shoulders to the ears. If the patient is unable to perform this action, he or she lies in the supine position to eliminate the effect of gravity and asked to repeat the test. Resistance is applied by the clinician in an attempt to depress the shoulders . Unilateral resistance can be applied to the posterior lateral aspect of the head while stabilizing the shoulder.
• Middle trapezius.The patient lies in the prone position with the shoulder joint abducted to 90 degrees, elbow extended, and the forearm in maximum supination so that the thumb is pointing to the ceiling ( Fig. 16-34) . The clinician applies pressure on the humerus by pushing toward the floor.
• Lower trapezius.The patient lies in the prone position, with the upper limb supported in the elevated position and aligned in the direction of the lower trapezius muscle fibers ( Fig. 16-35) . Grades 0–2 are determined by the firmness of the muscle contraction. Grades 2+ and 3− are based on how far the limb is lifted from the table. Grades 3–5 require the application of resistance by the clinician.

As discussed in the biomechanics section, proper scapular movement and stability are imperative for asymptomatic shoulder function. 24The serratus anteriorcan be assessed in a number of ways , including using the wall push-up. A more sensitive test involves putting the patient in the supine position with his or her shoulder flexed to 90 degrees and their elbow flexed. The patient is asked to protract the shoulder by lifting the elbow to the ceiling. Resistance is applied by the clinician at the hand, pushing downward ( Fig. 16-36). Given that the serratus anterior functions to control upward rotation of the scapula during arm elevation, this ability should also be assessed.

Finally, resisted elbow flexion and extension, as well as forearm supination (see Chap. 17), are examined to assess the biceps , brachialis , and tricepsfunction . Isometric elbow extension and flexion with the muscles in a stretched position will help exclude the biceps and triceps muscles. Pain reproduced with resisted elbow flexion could indicate a lesion to one or more of the elbow flexors, such as an intra-articular lesion of the LHB or a lesion in the sulcus of the LHB. The sulcus lesion can be tested with the patient side-lying, facing away from the clinician, and their arm hanging behind them. The clinician stabilizes the scapula and applies a longitudinal force along the humerus in a superior direction to drive the humerus superiorly. A positive sign is pain reproduced with this maneuver.

A painless weakness of elbow flexion can result from a fifth cervical root palsy, or a sixth cervical root palsy (a complete rupture of all of the elbow flexors is an extremely unlikely event.)

The wrist and hand are also evaluated for motor function as appropriate (see Chap. 18).

Examination of Movement Patterns

These tests are concerned with the coordination, timing, or sequence of activation of the muscles during movement. 206

Serratus Anterior

The patient lies in the prone position and is asked to perform a push-up and then return to the start position extremely slowly. The clinician checks for the quality of scapula stabilization. If the stabilizers are weak, the scapula on the side of impairment will shift outward and upward with a resultant winging of the scapula.

Shoulder Abduction

The patient sits with his or her elbow flexed to control the humeral rotation. The patient is asked to slowly abduct the arm. Three components are evaluated:

• Abduction at the G-H joint
• Rotation of the scapula
• Elevation of the whole shoulder girdle—the abduction movement is stopped at the point at which the shoulder begins to elevate; this typically occurs at approximately 60 degrees of G-H abduction

Functional Testing

The assessment of shoulder function is an integral part of the examination of the shoulder complex. Functional testing of the shoulder complex can include tests designed to detect a biomechanical dysfunction or tests designed to assess the patient's ability to perform the basic functions of ADL. Given the number of different shoulder conditions that exist, it is important to remember that each of the following functional tests may have specific limited applications.

Biomechanical Function

There are only two functional motions within the shoulder girdle: arm elevation using a combination of flexion and abduction and arm extension with adduction. All other motions of the shoulder are parts or composites of these two basic functional sets.

Basic Function Testing

By referring to Table 16-16, the clinician can determine the functional status of the shoulder for basic functions simply by measuring the amount of available ROM. For example, humeral motions necessary for eating and drinking have been reported at 5–45 degrees of flexion, 5–35 degrees of abduction, and 5–25 degrees of IR relative to the trunk. 292Combing hair has been found to require 112 degrees of arm elevation. 162

Mannerkorpi 293used three functional tests (hand-to-neck, hand-to-scapula, and hand-to-opposite scapula) to assess shoulder dysfunction in patients with fibromyalgia ( Table 16-17). Yang and Lin 294assessed the intertester and intratester reliability of these functional tests and found them to be reliable for documenting reduced function of the shoulder.

The assessment tool outlined in Table 16-18can also be used as a functional test of the shoulder. Several generic and region-specific outcome tools have been developed and used to document outcomes of patients with shoulder pathologies.

Shoulder Outcome Scales

A number of shoulder scales have been developed. Five of the most commonly used shoulder outcome scales are the University of California–Los Angeles (UCLA) shoulder scale, the simple shoulder test (SST), the shoulder pain and disability index (SPADI), the disabilities of the arm, shoulder, and hand (DASH), and the Penn Shoulder Score (PSS).

University of California–Los Angeles (UCLA) Shoulder Scale

The self-report section of the UCLA Shoulder Scale consists of two single-item subscales, one for pain and the other for functional level ( Table 16-19). The items are Likert-type (a psychometric scale) and scored from 1 to 10, with higher scores indicating less pain and greater function. 295

The Simple Shoulder Test

Lippitt et al. 296advocate the use of the SST ( Table 16-20). The SST is a standardized self-assessment of shoulder function consisting of 12 yes/no questions. The SST has high test and retest reproducibility and is sensitive to a wide variety of shoulder disorders. 296In addition, the SST has been shown to be a practical tool for documenting the efficacy of treatment for shoulder conditions. Patients without rotator cuff disease or other shoulder disorders are able to do all 12 functions of the SST. 196, 297– 299

When compared with other available shoulder self-assessment questionnaires, the SST has the highest test/retest reliability, takes the shortest amount of time for a patient to complete, is the easiest to score, and has satisfactory responsiveness. 300, 301The questions can be asked at the initial visit and then at subsequent visits to track progress.

Shoulder Pain and Disability Index. 302

The SPADI consists of two self-report subscales of pain and disability. The items of both the subscales are visual analog scales (VASs). The five-item pain subscale asks people about their pain during ADL, and each item is anchored by the descriptors “no pain” (left anchor) and “worst pain imaginable” (right anchor). The eight disability items ask people about their difficulty performing ADL. These items are anchored with the descriptors “no difficulty” (left anchor) and “so difficult it required help” (right anchor). Each item is scored by measuring the distance from the left anchor to the mark made by the person. Subscales are scored in a three-part process. First, item scores within the subscale are summed. Second, this sum is divided by the summed distance possible across all items of the subscale to which the person responded. Third, this ratio is multiplied by 100 to obtain a percentage. Higher scores on the subscale indicate greater pain and greater disability. To obtain the SPADI total score, the pain and disability subscales scores are averaged. 302

Disabilities of the Arm, Shoulder, and Hand

The acronym DASH was chosen to describe an outcome measure that reflects the impact on function of a variety of musculoskeletal diseases and injuries in the upper extremity. 303Items covered by the DASH questionnaire are symptoms and functional status. The components included under the concept of symptoms are pain, weakness, stiffness, and tingling/numbness. 303There are three dimensions under functional status: physical, social, and psychological status. Two versions of the DASH are available: a 30-item questionnaire that has optional three-question modules for sport/music and heavy work activities ( Table 16-21), and a 15–20-item questionnaire suitable for office use.