Knee dislocation

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Background

  • Popliteal artery injury occurs in ~25% of cases
    • neurologic injury/deficit may indicate vascular injury
  • Spontaneous reduction occurs in up to 50% of dislocations; often occurs prior to ED arrival
  • Types
    • Anterior (40%)
      • hyperextension mechanism
      • often involves PCL, ACL and either medial or lateral ligs are injured
    • Posterior (33%)
      • popliteal artery often injured
      • dash board injury
    • Lateral (18%)
    • Medial (4%)

Evaluation

Signs

  • Suggestive by severely injured knee that is unstable in multiple directions
  • lateral collateral ligament injured with peroneal nerve palsy = knee dislocation

Differential Diagnosis

Knee diagnoses

Acute Injury

Nontraumatic/Subacute

Associated Injuries

  • Nerve injury
    • Common peroneal nerve injury (25%)
      • Test for sensation in 1st dorsal web space, dorsiflexion of foot, extension of toes
    • Tibial nerve injured less often
  • Fractures
    • femur and tibia most common
    • check hip and ankle joints for associated fracture
    • avulsion fractures common
  • Compartment syndrome risk high with vascular compromise

Management

  • Reduce immediately
    • Posterior dislocation
      • Assistant holds distal femur and gently pulls counter-traction
      • Provider pulls proximal tibia longitudinally then anteriorly
      • Prevent additional arterial injury by limiting excessive force
    • Anterior dislocation
      • As above, but reversed. Provider pulls gently counter traction on proximal tibia while assistant pulls distal femure proximally then anteriorly
    • Splint in 10-15 degrees of flexion [1]
  • Vascular assessment
    • Assess popliteal and distal pulses
    • Measure ABIs
      • ABI >0.9 - serial exams
      • ABI <0.9 - arterial duplexes or CT angio
  • Monitor for compartment syndrome
    • no pulses: reduce immediately
    • no pulses post reduction: surgical exploration
      • ischemic time >8 hours has amputation rates as high as 86%
  • Neurological assessment
    • Peroneal nerve most commonly injured
      • Test for sensation in 1st dorsal web space, dorsiflexion of foot, extension of toes

Disposition

  • Institution will dictation admission process
    • Suggested algorithm
      • If: Strong pulses + ABI >0.9 + normal ultrasound, admit for obs and serial vasc exams
      • If: Good perfusion + asymmetric pulses or ABI <0.9 or abn U/S, consult vascular surgery + obtain CTA
      • If: Weak pulses or signs of ischemia = emergent vascular surgery consult and OR
  • Consider trauma consult depending on mechanism and additional injuries

References

  1. Davenport M. Procedures for orthopedic emergencies. In: Bond M, ed. Orthopedic Emergencies: Expert Management for the Emergency Physician. Cambridge: Cambridge University Press; October 31, 2013.


  • 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
  • AAOS Comprehensive Orthopaedic Review, Jay R. Leiberman. Published by American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2009
  • Levy BA, Fanelli GC, Whelan DB, Stannard JP, MacDonald PA, Boyd JL, Marx RG, Stuart MJ. Knee Dislocation Study Group. Controversies in the treatment of knee dislocations and multiligament reconstruction. J Am Acad Orthop Surg. 2009 Apr;17(4):197-206. http://www.ncbi.nlm.nih.gov/pubmed/19307669

See Also