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The anatomy of the shoulder (Figures 20-1 and 20-2) is complex because of the unconstrained nature of the joint, which allows an arc of motion greater than any other joint in the body. The shoulder is stabilized by both bony and soft tissue restraints (Table 20-1). The glenoid forms a small cup, which minimally constrains and stabilizes the humeral head (Figure 20-3). The glenoid labrum, a fibrocartilage lip, adds to the depth and width of the glenoid and is commonly injured in shoulder dislocations and in biceps tendon attachment injuries. The superior, middle, and inferior glenohumeral ligaments stabilize the shoulder through different arcs of motion, and are commonly injured along with the labrum in both adult and younger athletes.1

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Figure 20-1
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Anatomy of shoulder. (Used with permission from Van De Graaff KM. Human Anatomy. 6th ed. New York:McGraw Hill;2002:Figure 8-25, p 216.)

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Figure 20-2
Graphic Jump Location

Anatomy of shoulder. (Used with permission from Van De Graaff KM. Human Anatomy. 6th ed. New York:McGraw Hill;2002:Figure 8-25, p 216.)

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Table Graphic Jump Location
Table 20-1. Glenohumeral Stabilizers
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Figure 20-3
Graphic Jump Location

Anatomy of shoulder. (Used with permission from Van De, Graff KM. Human Anatomy, 6th ed. New York:McGraw Hill;2002:Figure 8-25, p 216.)

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The rotator cuff (Figures 20-4 and 20-5) provides secondary and dynamic stability to the shoulder, as do the periscapular muscles, which aid in stabilizing the shoulder and position it in space. There is some debate as to whether the biceps and its long head provide significant dynamic shoulder stability or not, but the biceps tendon and associated muscles are commonly injured in association with other patterns of shoulder injury. Although significant portion of shoulder motion is caused by the motion of the shoulder girdle itself, the scapula, the acromioclavicular (AC) joint, clavicle and the sternoclavicular (SC) joint, all contribute to the scapulothoracic and shoulder motion, and this needs to be addressed in detail when considering shoulder injuries. Basic movements of the shoulder are depicted and described in Figure 20-6.

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Figure 20-4
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Rotator cuff muscles (anterior view).

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Figure 20-5
Graphic Jump Location

Rotator cuff muscles (posterior view).

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