Occurs when the joint capsule of the shoulder becomes inflamed and stiff, making the joint difficult to move, often after prolonged immobilization of the shoulder. Pain is usually a constant and dull ache, worse at night, in colder weather, and during certain movements. This is not the same as arthritis or impingement syndrome.

The rotator cuff is made up of 4 muscles in the shoulder, the supraspinatus, infraspinatus, teres minor, and subscapularis. An injury to this region includes any type of irritation, swelling, inflammation, or damage to the muscles or tendons.