Posterior shoulder dislocation


Left shoulder and acromioclavicular joints with ligaments.
Shoulder anatomy, anterior.
Shoulder anatomy, posterior.
  • 2-4% of shoulder dislocations[1]
  • Complications (neurovascular injuries and rotator cuff tears) less common than in anterior dislocation
  • May go undetected for extended period as often missed on physical exam and imaging
  • Classically associated with seizures and lightning strikes

Shoulder dislocation types

Clinical Features

  • Posterior aspect of shoulder unusually prominent
  • Anterior aspect of shoulder appears flattened
  • Inability to rotate or abduct affected arm


  • Forceful internal rotation and adduction
    • Usually due to seizure or electric shock
  • Blow to anterior shoulder

Differential Diagnosis

Shoulder and Upper Arm Diagnoses



Refered pain & non-orthopedic causes:


Light bulb sign (left) with post-reduction comparison (right)
  • Plain film X-ray
    • Scapular "Y" view shows humeral head in posterior position
    • Lack of normal overlap of humeral head and glenoid fossa
    • "Light bulb sign" - fixed internal rotation makes for light bulb appearance of humeral head on AP
  • Consider CT for occult dislocations of evaluation of fractures
  • Bedside ultrasound can be used to assess for both dislocation and successful reduction


Closed reduction

Most require procedural sedation

  1. Adduct the arm
  2. Apply traction along long axis of humerus
  3. Have assistant push humeral head anteriorly into glenoid fossa
  4. Apply shoulder immobilizer
  5. Obtain post-reduction radiographs

Indications for Surgery

  • Lesser tuberosity displacement not reduced with reduction
  • Articular defect >25%
  • Dislocation >3 weeks
    • Do not reduce chronic dislocations in the ED due to risk of arterial injury; consult ortho for open reduction


  • Discharge after successful reduction
    • Maintain sling +/- swath or shoulder immobilizer (shoulder in adduction and internal rotation) until seen in follow-up by orthopedic surgery
  • Any patient with a chronic dislocation requires orthopedic consult in the ED for consideration of operative reduction due to the risk of arterial injury


  • Humerus fracture plus fracture of the posterior glenoid rim
  • Isolate fracture of lesser tuberosity
  • Reverse Hill-Sachs deformity
    • Impaction fracture of anteromedial humeral head

See Also

External Links


  1. Grate I Jr. Luxatio erecta: a rarely seen, but often missed shoulder dislocation. Am J Emerg Med. 2000 May;18(3):317-21.