If the rotator cuff muscles become fatigued from repetitive overhead motion, then they become less efficient in stabilizing the humeral head, and the labrum, capsule and cuff get over-stressed resulting in inflammation and pain. This is commonly referred to as glenohumeral instability.
Young athletes with glenohumeral instability will complain of pain in the front, back, top, or inside the shoulder with overhead activities. There may also be a sense of “shifting” or “popping.” Glenohumeral instability is treated with active rest, which means cutting back or avoiding painful activities until the pain resolves. Ice and anti-inflammatory medication may also help with pain control. Physical therapy to strengthen the rotator cuff complex as well as the entire shoulder girdle will provide the best chance for long-term recovery and a gradual return to throwing. The physical therapist will also evaluate the mechanics of the throwing motion to identify and correct any biomechanical flaws that are present. Physical therapy typically lasts 6-8 weeks for glenohumeral instability. Arthroscopic surgery to “tighten” the loose capsule may be indicated if physical therapy fails.
Volleyball and baseball are sports that often have athlete's with this type of injury.