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Condition/Disorder Synonyms

  • Shoulder impingement

  • Impingement syndrome shoulder

  • Subacromial compression

ICD-9-CM Code

  • 726.19 Other specified disorders of bursae and tendons in shoulder region

ICD-10-CM Code

  • M75.80 Other shoulder lesions, unspecified shoulder

Preferred Practice Pattern1

Key Features


  • Shoulder pain and dysfunction due to compression and abrasion of one or more of the rotator cuff tendons, the long head of the bicep tendon, and/or the subacromial bursa beneath the coracoacromial arch due to an abnormal mechanical relationship

  • The coracoacromial arch consists of the undersurface of the acromion, coracoacromial ligament as well as the undersurface of the acromioclavicular (AC) joint.

  • Impingement is the most commonly diagnosed shoulder problem and likely has numerous potential mechanisms, which can impact both treatment and prognosis.

Essentials of Diagnosis

  • Multifactorial and thought to be related to intrinsic and/or extrinsic mechanisms

    • Extrinsic mechanisms (extratendinous, cause decreased sub-acromial space and subsequent micro-trauma with repetitive movements)

      • Mechanical wear under the coracoacromial arch

      • Aberrant movement patterns due to rotator cuff and or periscapular muscular dysfunction

      • Capsular abnormalities

        • Capsular tightness (particularly posterior capsule)

        • Capsular laxity (poor humeral head dynamic control)

      • Sub-optimal posture

        • Muscle imbalances

      • Overuse/repetitive motions occurring above 90 degrees of elevation

    • Intrinsic factors (directly associated with the narrowing of the sub-acromial space)

      • Vascular supply/changes to the cuff tendons

      • Acromial morphology (structural variations).

        • Type I (flat)

        • Type II (curved)

        • Type III hooked)

      • Degenerative and/or structural changes to the AC joint

      • Other trophic changes in the coracoacromial arch or humeral head

  • Classification

    • Primary impingement is usually associated with degenerative changes to any of the following tissues:

      • Rotator cuff tendons

      • AC joint

      • Coracoacromial arch

    • Secondary Impingement is the result of muscle imbalances and/or joint instability, which can result in altered dynamics and subsequent secondary impingement.

    • Neer stages

      • Stage I: Edema and hemorrhage of the subacromial bursa; patient is generally <25 years of age

      • Stage II: Histologic changes of tendinosis to the effected tendons; patient usually between 25 to 40 years of age

      • Stage III: Partial or complete rupture of the cuff and or bicep tendons and potential associated changed to the acromion and AC joint; patient usually >40 years of age.

    • Third class of impingement, not subacromial in nature: internal impingement

      • Occurs between the undersurface (articular side) of the rotator cuff tendons and the posterior/superior surface of the labrum in the position of abduction and external rotation that occurs with throwing.

    • Regardless of classification, all types of impingement are proposed to be mechanisms of rotator cuff and biceps tendinopathy

    • Treatment varies based on impingement type, contributing factors, and associated tissue quality.

    • Diagnosis is usually made by clinical examination and often accompanies 3 or more special tests2

      • Neer's impingement test

      • Hawkins-Kennedy impingement sign/test

      • Passive horizontal ...

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