The Scapula and its Muscles

9. Rotator Cuff

The rotator cuff is a group of four muscles, along with corresponding tendons and ligaments, that hold the humerus to the scapula. This group originates from the scapula and helps stabilize the shoulder. The supraspinatus muscle comes from the upper section of the scapula, and it is responsible for arm abduction -- the ability to raise the arm from the side to a T position. The infraspinatus muscle helps with external rotation of the humerus, while the teres minor muscle prevents the head of the humerus from slipping upward during the reverse movement. The subscapularis muscle prevents displacement of the humerus head.