Rotator cuff injuries are injuries to the four muscles that collectively form the rotator cuff: the teres minor, supraspinatus, infraspinatus, and subscapularis muscles. These muscles and their attaching tendons are responsible for supporting and stabilizing the glenohumeral, or shoulder, joint. Specifically, they help hold the ball-shaped head of the humerus bone of the upper arm in the cavity of the shoulder blade known as the glenoid fossa. As such, rotator cuff injuries will affect function in the shoulder joint and therefore severely limit movement of the arm.
The supraspinatus is the topmost of the four, running horizontally from the top of the shoulder blade to the top of the humerus, with the infraspinatus found parallel to and just beneath the supraspinatus. Located below this is the teres minor, which originates lower on the shoulder blade and runs somewhat diagonally to attach at the top of the humerus below the other two muscles. The subscapularis is the only one of the four located on the ventral or front side of the shoulder blade, and it is triangular in shape, its narrowest point inserting beneath the other muscles at the top of the humerus.
Rotator cuff injuries most commonly affect the tendons that connect these muscles to the shoulder joint. One such injury is tendinitis, which is caused by overuse of the rotator muscles through repeated stress on the shoulder joint and is common in athletes that perform repetitive throwing motions, such as baseball pitchers. Tendinitis is an inflammation of the attaching tendons that can become very painful and difficult to eliminate without adequate rest of the shoulder joint and avoidance of the movement patterns that caused it to develop. In addition to rest, treatment generally includes icing the joint and taking over-the-counter anti-inflammatories like ibuprofen.
Tears are another common type of rotator cuff injury. They are either caused by repetitive movements that break down the tendon to the point of tearing, or through a specific trauma to the shoulder. Rotator cuff tears can be much more debilitating than tendinitis, requiring immobilization of the arm until the injury heals. Compression, or wrapping, of the joint may also be recommended to reduce both movement and swelling, as may regular icing.
A final category of rotator cuff injury is impingement, which occurs when one or more muscles is pinched against the shoulder blade, typically as a result of prolonged muscle imbalance that leads to postural defects. As with any of the rotator cuff injuries, impingement can be treated as well as prevented with regular strengthening exercises to restore the upper body’s normal alignment and achieve optimum function. These exercises may include holding a lightweight dumbbell or pulley and externally rotating the shoulder joint, as internal rotation is the most common imbalance. A highly recommended version of this exercise requires lying on one’s side with a dumbbell and, with elbow held tightly to one’s side and bent 90 degrees, rotating the shoulder inward and outward to lift and lower the dumbbell. This movement targets all four muscles of the rotator cuff.