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Knee dislocation
From WikEM
Contents
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%)
Clinical Features
- Suggested by severely injured knee that is unstable in multiple directions
- Lateral collateral ligament injured with peroneal nerve palsy = knee dislocation
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
- Common peroneal nerve injury (25%)
- Fractures
- Femur and tibia most common
- Check hip and ankle joints for associated fracture
- Avulsion fractures common
- Compartment syndrome risk high with vascular compromise
Differential Diagnosis
Knee diagnoses
Acute Injury
- Knee fractures
- Patella fracture
- Tibial plateau fracture
- Knee dislocation
- Patella dislocation
- Segond fracture
- Meniscus and ligament knee injuries
- Patellar Tendinitis (Jumper's knee)
- Patellar tendon rupture
- Quadriceps tendon rupture
Nontraumatic/Subacute
- Septic Joint
- Gout
- Popliteal cyst (Baker's)
- Prepatellar bursitis (nonseptic)
- Septic bursitis
- Pes anserine bursitis
- Patellofemoral syndrome (Runner's Knee)
- Patellar Tendinitis (Jumper's knee)
- Osgood-Schlatter disease
- Arthritis
Evaluation
- Knee x-ray (to rule-out fracture); consider CT
- Vascular assessment
- Assess popliteal and distal pulses
- Measure ABIs
- ABI >0.9 - serial exams
- ABI <0.9 - arterial duplexes or CT angio
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]
- Posterior dislocation
- 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
- Peroneal nerve most commonly injured
Disposition
- Institution will dictation admission process
- Suggested algorithm
- If: Strong pulses + ABI >0.9 + normal doppler, admit for obs and serial vascular exams
- If: Good perfusion + asymmetric pulses or ABI <0.9 or abnormal doppler, consult vascular surgery + obtain CTA
- If: Weak pulses or signs of ischemia = emergent vascular surgery consult and OR
- Suggested algorithm
- Consider trauma consult depending on mechanism and additional injuries
References
- ↑ 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
