The rotator cuff is a group of four muscles and their tendons that wrap around to form a "cuff" over the upper end of the arm at the shoulder. The rotator cuff helps guide the shoulder through many motions by allowing lift and rotation to the arm while stabilizing the ball of the shoulder within the socket. Tendonitis of the rotator cuff, a common condition, is inflammation of the tendons and bursa (bursitis) and occurs with repetitive overhead activity or overuse of the arm. Unfortunately, a rotator cuff tear is not an uncommon problem and is a frequent cause of disability and pain in the adult population. A rotator cuff tear occurs when there is a tear or injury to one of the rotator cuff tendons.