Knee dislocation

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 knee injury

• Knee dislocation
• Knee fractures
  • Patella fracture
  • Segond fracture
  • Tibial plateau fracture
• Meniscus and ligament knee injuries
• Patella dislocation
• Patellar tendonitis
• Patellar tendon rupture
• Quadriceps tendon rupture

Nontraumatic/Subacute

• Arthritis
• Gout and Pseudogout
• Osgood-Schlatter disease
• Patellofemoral syndrome (Runner's Knee)
• Patellar tendonitis (Jumper's knee)
• Pes anserine bursitis
• Popliteal cyst (Bakers cyst)
• Prepatellar bursitis (nonseptic)
• Septic bursitis
• Septic joint
• DVT

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
• 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

• 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

• Knee (Main)