All four of the rotator cuff muscles (RTC) attach from the shoulder blade (scapula) to the arm bone (humerus). Although the RTC is responsible for turning the arm in and out (internal and external rotation) when it is hanging down by your side, its main function is to pull and hold the ball (head) of the humerus into the socket (glenoid fossa) thereby allowing the humeral head to freely rotate in the glenoid fossa which gives us that great shoulder range of motion. But that increased range of motion leads to greater chance of injury and when the RTC is injured, as in a rotator cuff tear, it allows excess ‘sloppy movement’ (translation), causing pain, further damage, muscle imbalances, and compensations. Keeping the RTC strong and healthy is usually easily accomplished. If you have questions on how to increase your RTC strength, ask Mike, Chip, or Sharon.
Shoulder – Front View (Wikipedia) Shoulder Back View (Wikipedia)