Patella dislocation

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Background

  • Typically occurs with trauma to an extended knee with externally rotated foot[1]
  • Acute dislocation occurs with traumatic injury, M=F, may see hemarthrosis[2]
  • Chronic dislocation seen more commonly in women/teenage girls, typically little or no swelling[2]
  • Common associated fractures
    • Medial patella facet
    • Lateral femoral condyle

Clinical Features

patella dislocates laterally
  • Patella is usually displaced laterally; knee is held in flexion

Differential Diagnosis

Knee diagnoses

Acute knee injury

Nontraumatic/Subacute

Evaluation

Patellaluxation ap 001.png
  • Clinical diagnosis
  • May consider pre-reduction x-ray if concern for fracture (not required)

Management

Relocation with lateral pressure on dislocated patella
  • Reduce; do not need x-rays prior to reduction. Rarely need any sedation though a dose of IV pain medication can help relax the patient
    • Option #1:
      • Mild flexion of hip (20-30 degrees by raising head of bed, not by propping the leg up off the bed) to relax quadriceps
      • Slowly extend and slightly hyperextend the knee and slide patella back into place.
    • Option #2
      • One provider applies slow downward pressure over the quads. This stretches out the muscle and slowly straightens the leg
      • At the same time, second provider pulls gentle traction of the patella outward while rotating the patella back over from lateral to anterior
  • Knee immobilizer, NSAIDs, weight-bearing as tolerated

Disposition

  • Obtain ortho consult if unable to reduce or fracture/loose bodies seen on post-reduction x-ray
  • Otherwise may be discharged with ortho follow-up in 1-2 weeks

References

  1. Review of Orthopaedics, 6th Edition, Mark D. Miller MD, Stephen R. Thompson MBBS MEd FRCSC, Jennifer Hart MPAS PA-C ATC, an imprint of Elsevier, Philadelphia, Copyright 2012
  2. 2.0 2.1 Fithian DC, Paxton EW, Stone ML, Silva P, Davis DK, Elias DA, White LM. Epidemiology and natural history of acute patellar dislocation. AJSM 2004;32:1114-1121

See Also

Knee (Main)