Assessment of the shoulder in rotator cuff tears

Abstract

The rotator cuff consists of four muscles; the subscapularis, supraspinatus, infraspinatus, and teres minor. The long head of the biceps tendon is another important component of the complex. The subscapularis is a head depressor, and in certain positions an internal rotator. The infraspinatus and teres minor are external rotators. The conjoint tendon of these muscles, attached to the tuberosities, anatomically and functionally, works as a unit, to maintain dynamic glenohumeral stability centering the humeral head onto the glenoid articulation. The long head of the biceps attaches to the supraglenoid tubercle of the glenoid and has a stabilising and depressing action on the humeral head. The rotator cuff gives 50% of the abductor power and 80% of the external rotator power to the gleno-humeral joint.