Supraspinatus

The Supraspinatus lies deep to the trapezius muscle. It originates from the medial aspect of the supraspinous fossa of the scapula and narrows into a strong tendon before inserting into the superior facet of the greater tubercle of the humerus.

The supraspinatus tendon is prone to rupture during middle and later life as a result of attrition or sudden strain. Due to the fusion of the supraspinatus tendon and the capsule of the shoulder joint, rupture of the tendon allows direct communication between the subacromial bursa and the synovial cavity of the shoulder joint. The most commonly torn "rotator cuff" muscle is the supraspinatus. The supraspinatus muscle initiates abduction of the arm and helps protect the shoulder joint by keeping the head of the humerus in place. Its function may be evaluated with the drop arm test.