The rotator cuff is a group of muscles and tendons in your shoulder. They help you lift and move your arms away from your body. The rotator cuff keeps the ball of the upper arm bone (humerus) in the shoulder blade socket.
A partial or complete rotator cuff tear makes it difficult to raise and move your arm. You may have shoulder pain and arm weakness. Rotator cuff injuries are common, especially as you get older. Some people need surgery to reattach a torn rotator cuff.