Patella dislocation

Background

  • Usual mechanism is blow to extended knee with externally rotated foott[1]
  • May also occur with sudden lateral cut or twisting at the ankle or knee
  • Acute traumatic dislocations more common in males[2]
  • Chronic dislocation seen more commonly in women/teenage girls, typically little or no swelling[2]
    • May be associated with hemarthrosis
  • Chronic dislocation more common in females
    • Typically little or no swelling

Clinical Features

patella dislocates laterally
  • Patella usually displaced laterally
  • Knee held in flexion
  • Pain

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
    • Generally do not need x-rays prior to reduction
    • Sedation rarely required
      • Single dose of pain medication may facilitate relaxation

Techniques for closed reduction

  • Single operator
  1. Place the hip in mild flexion by raising head of bed
    • This facilitates relaxation of the quadriceps
  2. Gently extend the knee with one hand while pushing the patella back in place with the other hand
  • Two operators
  1. One provider applies slow downward pressure over quadriceps
    • This stretches the muscle and slowly straightens the leg
  2. Second provider gently rotates the patella lateral to anterior
  • Place patient in knee immobilizer
  • Provide NSAIDs
  • Obtain radiographs to rule out associated fracture
  • Allow weight-bearing as tolerated

Complications

  • Commonly associated fractures:
    • Medial patellar facet
    • Lateral femoral condyle

Disposition

  • If unable to reduce or if fracture or loose bodies are seen on post-reduction radiographs, consult orthopedic surgery
  • If patella successfully reduced, discharge with knee immobilizer and orthopedic follow up within 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)