Posterior Shoulder Instability

Posterior shoulder instability — where the humeral head displaces posteriorly — accounts for approximately 5–10% of all shoulder instability. It is most common in weight lifters (bench press), football linemen, and swimmers, and is frequently missed because the presentation is less dramatic than anterior instability. Voluntary posterior subluxation (intentional self-positioning of the shoulder to cause it to slip) is a distinct entity often associated with psychological factors.

Pain and a "dead arm" sensation with the arm in forward flexion, adduction, and internal rotation — the "at-risk" position for posterior instability. The posterior load-and-shift test and the jerk test confirm posterior laxity. MRI arthrography evaluates the posterior capsule, posterior labrum (reverse Bankart), and glenoid retroversion.

Cases unresponsive to 6 months of dedicated rehabilitation in which structural posterior labral tears are confirmed on imaging are considered for surgical repair.

External patient-education references and related OSI pages for additional background:

• Britannica — Dislocation
• Britannica — Shoulder (anatomy)
• AAOS OrthoInfo — patient education library
• OSI glossary — orthopedic terminology in plain language