Rotator Cuff Tendonitis
Ross Hauser, M.D.

Rotator cuff tendonitis may occur  when the muscles of the rotator cuff, which include the supraspinatus, infraspinatus, teres minor, and subscapularis, are overworked causing the tendon to become inflamed and painful. The more common scenario of RCT occurs when a chronically unstable shoulder forces the muscles of the shoulder, especially the rotator cuff muscles and tendon, to work beyond their capabilities to stabilize the shoulder as it moves through its complex motions. These small rotator cuff muscles were not designed to stabilize the shoulder or perform the major work in shoulder motion, but instead should function to perform shoulder rotation.

The important point for the athlete is to remember that pain is your body telling you that something is wrong. The time to get treatment is not when your shoulder finally goes out, but when the pain first starts. Shoulder problems either manifest as shoulder pain or weakness. A pitcher feeling weak requires shoulder examination.

Pain and/or weakness are common signs of ligament weakness. Ligament weakness in the shoulder will almost always lead to a rotator cuff tendonitis. If this is not treated, the rotator cuff muscles will give out, putting even more stress and strain on the ligaments. Eventually shoulder instability develops.

Rotator Cuff Tendonitis and Impingement Syndrome
Rotator cuff tendonitis occurs when the small muscles of the rotator cuff, the supraspinatus, infraspinatus, teres minor, and subscapularis, become strained causing weakness of these structures and subsequent tendonitis. While the deltoid muscle is the big and strong muscle of the shoulder, as seen on many well-built athletes, the small and relatively weak rotator cuff muscles perform key functions. The supraspinatus helps seat the humeral head (ball) into the glenoid cavity (socket) when the arm is raised from the side (abducted).

Rotator Cuff Impingement
The rotator cuff can get "pinched" between the humeral head and acromion when the arm is raised to the side.

The infraspinatus and teres minor rotate the forearm away from the body or in the hand-waving position (external rotation), and the subscapularis rotates the forearm towards the body (internal rotation). Once the balance between motion and joint stability is altered through weakness in the static structures (ligaments) or the dynamic structures (rotator cuff muscles), pain and impaired function will invariably ensue.1

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