The rotator cuff is a group of muscles and tendons that cover the top of your upper arm bone and help you rotate your shoulder. Rotator cuff injuries are quite common. Millions of Americans visit a doctor every year because of a rotator cuff disorder. Such injuries may be due to inflammation, infection, or a tear in the muscle or tendon. Excessive, repeated, overhead movements, such as those performed during swimming or playing tennis, can lead to a rotator cuff injury. Damage to the rotator cuff makes it difficult for you to lift your arm and reach above your head. Follow the links below to find WebMD's comprehensive coverage about how rotator cuff injuries occur, what the symptoms are, how to treat them, and much more.