A 75 yo M presents to the ED after a fall down several steps at home. He is complaining of severe R knee pain. On exam, there is an obvious deformity to his R knee. He does not have a palpable DP pulse. An x-ray is obtained. What's the diagnosis? (scroll down for answer)

Answer: Posterior knee dislocation

• Knee dislocations are orthopedic emergency
• High energy mechanisms- MVC, fall from height, athletic injury
• Can be anterior, posterior, medial, lateral or rotary
• May be reduced spontaneously prior to evaluation
• Associated w/ popliteal artery injury in up to 45% cases
• Requires emergent vascular consult for any signs of ischemia
• CTA should be obtained for evaluation of vascular injury
• Also associated w/ peroneal nerve injury, rupture of multiple ligaments, and femur/tibial fracture

References : Gebauer, Gregory, and John H Wilckens. “Knee Dislocation.” 5 Minutes Orthopaedic Consult, edited by Frank J Frassica et al., 2nd ed., Lippincott Williams & Wilkins, 2018.