The rotator cuff is a functional unit of four muscles and their tendons surrounding the shoulder joint. It comprises the supraspinatus, infraspinatus, teres minor and subscapularis muscles.
Their joint task is to centre the head of the humerus in the comparatively flat shoulder socket, enabling controlled movement in all directions. In addition, each muscle performs specific rotation and lifting movements, for example external rotation by the infraspinatus and teres minor or internal rotation by the subscapularis.