Functional anatomy of the shoulder complex.

The shoulder complex, together with other joint and muscle mechanisms of the upper limb, primarily is concerned with the ability to place and control the position of the hand in the visual work space in front of the body. The shoulder mechanism provides the upper limb with a range of motion exceeding that of any other joint mechanism. The placement of the hand is determined by four components of the shoulder complex: the glenohumeral, acromioclavicular, and sternoclavicular joints and the scapulothoracic gliding mechanism. The clavicular joints permit the scapula to move against the chest wall during movements of the arm, allowing the glenoid fossa to follow the head of the humerus, and thus contribute significantly to total arm movement. The functional interrelationships between the glenohumeral, scapulothoracic, and clavicular joint mechanisms are critical in providing a full, functional ROM. Any pathological condition of any one of these mechanisms will disturb upper limb function. The ligamentous and periarticular structures of the shoulder complex combine in maintaining the joint relationships, withstanding the forces applied to the joint surfaces, and stabilizing the dependent limb.