After completion of this chapter, the physical therapist should be able to do the following:
FUNCTIONAL ANATOMY AND BIOMECHANICS
The anatomy of the shoulder joint complex allows for tremendous range of motion (ROM). This wide ROM of the shoulder complex proximal permits precise positioning of the hand distally, to allow both gross and skilled movements. However, the high degree of mobility requires some compromise in stability, which, in turn, increases the vulnerability of the shoulder joint to injury, particularly in dynamic overhead athletic activities.1
The shoulder girdle complex is composed of three bones—the scapula, the clavicle, and the humerus—that are connected either to one another or to the axial skeleton or trunk via the glenohumeral joint, the acromioclavicular joint, the sternoclavicular joint, or the scapulothoracic joint (Figure 20-1). Dynamic movement and stabilization of the shoulder complex require integrated function of all four articulations if normal motion is to occur.2
Skeletal anatomy of the shoulder complex
(Reproduced with permission from Prentice. Principles of Athletic Training, 16th ed. New York, NY: McGraw Hill; 2017.)
The clavicle articulates with the manubrium of the sternum to form the sternoclavicular joint, the only direct skeletal connection between the upper extremity and the trunk. The sternal articulating surface is larger than the sternum, causing the clavicle to rise much higher than the sternum. A fibrocartilaginous disc is interposed between the two articulating surfaces. It functions as a shock absorber against the medial forces and also helps to prevent any displacement upward. The articular disc is placed so that the clavicle moves on the disc, and the disc, in turn, moves separately on the sternum. The clavicle is permitted to move up and down, forward and backward, in combination, and in rotation.
The sternoclavicular joint is extremely weak because of its bony arrangement, but it is held securely by strong ligaments that tend to pull the sternal end of the clavicle downward and toward the sternum, in effect anchoring it. The main ligaments are the anterior sternoclavicular, which prevents upward displacement of the clavicle; the posterior sternoclavicular, which also prevents upward displacement ...