Athletes, workers and anyone who uses their shoulder for overhead activities often suffer shoulder pain caused by excessive rubbing or squeezing (impingement) of the rotator cuff and shoulder blade. The rotator cuff is a group of muscles and tendons that stabilizes the shoulder and permits lifting and rotating movements. If the rotator cuff weakens or is injured, the bone of the upper arm can lift up, pinching the rotator cuff against the shoulder blade.
In addition to rotator cuff injuries such as tendonitis and tearing, impingement may be the result of bursitis, an inflammation of the cushioning sac between the rotator cuff and the shoulder blade. A torn rotator cuff is a potential outcome of shoulder impingement.