Podcast #148: Knee Dislocation - The Emergency Medical Minute

Podcast #148: Knee Dislocation

4ecce1c5-678a-4ad3-be1e-06469ce3fd90Run Time:  4 minutes

Author: Samuel Killian M.D.

Educational Pearls:

  • A true knee dislocation and a patellar dislocation are slightly different conditions. A true knee dislocation is the translation of the femur and the tibia – described as anterior/posterior, posterior/anterior, medial/lateral.
  • Knee dislocations occur after a high force blow to the leg.
  • 50% of the time the knee can be self-reduced or naturally reduced prior to presentation to the ED. Otherwise the knee dislocation is totally obvious.
  • The big concern with a knee dislocation is vascular or nerve injury.
  • Popliteal artery injury occurs approximately 50% of the time. Normally this is evaluated by feeling for pulses, assessing discoloration, but 10% of cases can have normal pulses with serious injury.
  • Patients with popliteal artery injury may need emergent revascularization surgery if there are hard signs of vascular injury.
  • If a patient has no hard signs of vascular injury then ABI (ankle-brachial index) is used to assess the likelihood of injury – ABI of >.9 then there is 95% sensitivity for no significant arterial injury, ABI of <.9 then it is highly likely that there is significant arterial injury.
  • 30% of knee dislocations have peroneal nerve injury, which presents as numbness in 1st web space or trouble with dorsal flexion, however this may be hard to assess due to the patient’s pain.

References: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC535529/

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