Recurrent posterior instability of the shoulder is much less common than anterior instability. The incidence of posterior instability is reportedly between 2% and 12% of all shoulder instabilities (1, 2). Historically, management of posterior shoulder instability has been complicated by recurrence rates ranging from 7% to 72% with operative management and 16% to 96% with nonoperative management (2, 3, 4). Many of the failures with operative treatment have been attributed to unrecognized multidirectional instability (5). Nonoperative management comprises a formal physical therapy program with emphasis on strengthening of the posterior deltoid, infraspinatus, and teres minor (6). Arthroscopic management of this difficult problem continues to evolve. Several authors have demonstrated successful arthroscopic augmentation of the glenolabral concavity, reduction of capsular laxity, and repair of traumatic labral lesions of the posterior glenoid (1, 7, 8, 9).

Patients with posterior instability often present with positional symptoms, in which posterior subluxation of the humeral head occurs when the arm is adducted at 90 degrees of flexion. These patients typically present with posterior shoulder pain with or without distinct symptoms of instability. Biomechanical evaluation of posterior shoulder translation has demonstrated a continuum between subluxation and dislocation (10). Pain is exacerbated by activities that posteriorly load the shoulder in the adducted position (bench press or push-up exercises) (5, 8). Most commonly, trauma to the affected extremity (fall onto an outstretched arm, blow to a forward-flexed adducted arm) precedes the onset of symptoms. However, patients rarely report a history of frank posterior dislocation (2, 8). The etiology of the injury may also be attributed to chronic overuse that leads to microtrauma and the development of laxity of the capsulolabral complex (4, 7). Athletic activities that predispose the individuals to posterior capsulolabral injury include baseball, softball, football, swimming, and volleyball (5, 11).