The rotator cuff is a group of four muscles that attach the humerus to the shoulder and stabilize the joint as the shoulder lifts and rotates. When the tendons in the region tear, it can result in shoulder pain and weakness that severely impair a person’s ability to perform activities of daily living. The two main causes of rotator cuff tears are acute injury and degeneration. Degenerative tears are much more common and occur as the tendon wears down over time. Acute tears may happen when a person falls on an outstretched arm or attempts to lift something too heavy using a jerking motion. Acute tears also may result from other injuries such as collarbone fractures or shoulder dislocations. Other factors that may contribute to the development of a rotator cuff tear include repetitive stress or motion in the shoulder, inadequate blood supply, and bone spurs. People over the age of 40 are at the greatest risk for rotator cuff tears. Other high-risk groups include people who perform repetitive lifting activities (especially overhead lifting), athletes in sports such as tennis and baseball, and people whose job function involves constant overhead motion (e.g., painters and carpenters). In young people, most rotator cuff tears occur as the result of traumatic injury. Treatment of rotator cuff tears varies depending on the type and severity of the injury and may include rest, modification of daily activities, administration of anti-inflammatory medications, steroid injection, and participation in a physical therapy program to restore movement and strengthen the shoulder. If the symptoms do not improve with non-surgical treatment, surgery may be necessary to reattach the tendon to the humerus.