The rotator cuff is a major structure inside the shoulder. The muscles of the rotator cuff attach to the front and back surfaces of the shoulder blade while the tendons attach to the upper ball portion of the humers. The cuff of tendon tissue rotates the humerus - hence the catchy name - rotator cuff.

The most important component of the rotator cuff for the golf swing is the subscapularis muscle/tendon (arrow) which helps rotate the arm inward. So-called rotator cuff impingement occurs when the cuff tendon rubs up against the undersurface of the upper part of the shoulder blade (star).