The rotator cuff is the thick band of muscles and tendons that covers the top of the upper arm and holds in it place, providing stability and a full range of motion to the shoulder joint. It is made of four muscles and their associated tendons. These tendons can become partially or completely torn as a result of a rotator cuff tear. A rotator cuff tear most often occurs as a result of overuse of the muscles over a long period of time. As a result, this condition is most common in patients over the age of 40. It may also occur as a result of a traumatic injury, and involves pain when lifting or lowering their arm, muscle weakness and atrophy.