Posterior Shoulder Instability and Sport Activities

Posterior shoulder instability in athletes and the sports-active population can be an important factor for disability and lesser performance than expected. Two main groups of patients with different injury etiology and different pathomechanics should be differentiated. They also differ each from other in their participating sport. Contact athletes are exposed to traumatic events and repetitive microtrauma with overload to the posterior part of the glenohumeral joint. Traumatic posterior shoulder dislocation or subluxation can be result of the force applied in the posterior direction. On the other hand, repetitive microtrauma to the posterior shoulder complex, which is the most frequent cause of posterior shoulder instability, is the result of the continuous loading to the posterior glenohumeral restraints. The second group are overhead athletes, where the origin of posterior shoulder instability is mainly atraumatic, with gradually developed pain and a sensation of unstable shoulder. In these cases, concomitant injuries and pathological findings in addition to posterior shoulder instability are common. The connection between labral lesion, dynamic shoulder dysfunction, and capsular laxity can be described as a vicious circle. Microinstability events in a decompensated shoulder with excessive laxity leads to progression of labral lesions. Adaptive mechanisms in the glenohumeral joint specific for overhead athletes may challenge the diagnosis as the examiner must differentiate between adaptive capsular laxity and pathological instability. Prevention and conservative approach should be the first treatment option, especially in overhead athletes. Good indications for surgical treatment are structural pathological changes to the posterior capsulolabral complex in cases of traumatic posterior shoulder instability.