The rotator cuff is a group of four small muscles that stabilise the shoulder by approximating the head of the humerus (upper arm bone) in the socket (of the shoulder blade). The rotator cuff also has a role in movement of the arm. The four muscles include the supraspinatus, teres minor, subscapularis and infraspinatus.
A rotator cuff strain or tear can affect one or more of the tendons of the rotator cuff. Tears can occur traumatically as a result of forceful movements such as falls, pulling of the arm and lifting heavy loads quickly or as the result of long term degeneration.