The 4 muscles and tendons of the rotator cuff are called the supraspinatus, subscapularis, teres major, and infraspinatus. These tendons and muscles work together to stabilize the glenohumeral joint and move the humerus in the shoulder socket.
The supraspinatus is the rotator cuff muscle that is most frequently torn. Tears start to become common beyond the age of forty, with an increased incidence in each decade of life. Figure 3 illustrates a supraspinatus rotator cuff tear.