In anatomy, the rotator cuff (sometimes incorrectly called a “rotator cup”, “rotor cuff”, or “rotary cup”) is a group of muscles and their tendons that act to stabilize the shoulder. The four muscles of the rotator cuff are over half of the seven scapulohumeral muscles. The four muscles are the supraspinatus muscle, the infraspinatus muscle, teres minor muscle, and the subscapularis muscle.