In the normal situation, the ball is kept in the center of the socket by the ligaments and rotator cuff tendons. There are four rotator cuff tendons: one in the front of the ball (the subscapularis muscle and tendon), one larger one in the back of the shoulder (the infraspinatus muscle and tendon), one smaller one in the back of the shoulder (the teres minor muscle and tendon) and one on the top of the shoulder (the supraspinatus muscle and tendon).