As the name implies, the rotator cuff muscles combine to form a cuff around the top of the humerus, which is the arm bone that inserts into the shoulder joint. These muscles stabilize and control the shoulder as it moves. There are also various tendons underneath the bony point of the shoulder. Ligaments in the region help further protect these tendons. The rotator cuff is prone to tears, tendonitis, impingement, and other injuries, collectively known as rotator cuff syndrome. The effects of such injuries range from mild inflammation to partial and total tears, which may necessitate surgical repair. Pain may be present when the arm is at or above shoulder height, when lying on the affected shoulder, when reaching or lifting, when moving the hand behind the back or head, and in the most severe cases, when immobile. The most accurate method of diagnosing injuries of the rotator cuff is performing an ultrasound. Treatment of rotator cuff injuries will vary depending on the type and severity of the injury and may include administration of pain relief and anti-inflammatory medications and participation in a physical therapy program focused on regaining range of motion and restoring muscle strength and control. In severe cases, surgery may be necessary.