Rotator Cuff

The four muscles that make up the rotator cuff are supraspinatus, infraspinatus, teres minor, and subscapularis. Subscapularis inserts on the lesser tubercle of the humerus while the other three muscles insert onto the greater tubercle.

It is believed that swimmer's shoulder is caused by the impingement of the tendon of the supraspinatus muscle as it passes through the subacromial space. This also makes the supraspinatus more suspectible to tear.

Thanks to Honglin!