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Objectives
To identify on a human skeleton or human subject selected bony structures of the shoulder joint
To label on a skeletal chart selected bony structures of the shoulder joint
To draw on a skeletal chart the muscles of the shoulder joint and indicate, using arrows, shoulder joint movements
To demonstrate with a partner all the movements of the shoulder joints and list their respective planes and axes of rotation
To learn and understand how movements of the scapula accompany movements of the humerus in achieving movement of the entire shoulder complex
To determine, list, and palpate the muscles of the shoulder joint and their antagonists and appreciate the role of the ligaments in providing stability
To organize and list the muscles that produce the movements of the shoulder girdle and the shoulder joint
To learn and understand the innervation of the shoulder joint muscles
To determine, through analysis, the shoulder joint movements and muscles involved in selected skills and exercises
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The only attachment of the shoulder joint to the axial skeleton is via the scapula and its attachment through the clavicle at the sternoclavicular joint. Movements of the shoulder joint are many and varied. It is unusual to have movement of the humerus without scapula movement. When the humerus is flexed above shoulder level, the scapula is elevated, rotated upward and abducted. With glenohumeral abduction above shoulder level, the scapula is elevated and rotated upward. Adduction of the humerus results in depression and rotation downward, whereas extension of the humerus results in depression, rotation downward and adduction of the scapula. The scapula abducts with humeral internal rotation and horizontal adduction. The scapula adducts with external rotation and horizontal abduction of the humerus. For a summary of these movements and the muscles primarily responsible for them, refer to Table 5.1.
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Because the shoulder joint has such a wide range of motion in so many different planes, it also has a significant amount of laxity, which often results in instability problems such as rotator cuff impingement, subluxations and dislocations. The price of mobility is reduced stability. The concept that the more mobile a joint is, the less stable it is and that the more stable it is, the less mobile it is, applies generally throughout the body, but particularly in the shoulder joint. See the section on stability and mobility of diarthrodial joints in Chapter 1.
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