Contributor: Erik Verzemnieks, MD

Educational Pearls:

• Knee dislocations are most common in high energy trauma, such as a motor vehicle accident
• The knee may appear grossly normal on initial inspection since dislocations can spontaneously reduce - Look for such findings as hemarthrosis, instability, or ecchymosis, as clues to an occult dislocation.
• Knee dislocations are often associated with damage to the popliteal artery that runs behind the knee.
• Assess for pulse deficit on exam. If you are concerned - use the ankle-brachial index (normal >0.9). If the ABI is abnormal, evaluate with CT angiogram and a vascular surgery consult.

References

Mills WJ, Barei DP, McNair P. The value of the ankle-brachial index for diagnosing arterial injury after knee dislocation: a prospective study. J Trauma. 2004 Jun;56(6):1261-5.

Steele HL, Singh A. Vascular injury after occult knee dislocation presenting as compartment syndrome. J Emerg Med 2012; 42:271.

Sillanpää PJ, Kannus P, Niemi ST, et al. Incidence of knee dislocation and concomitant vascular injury requiring surgery: a nationwide study. J Trauma Acute Care Surg 2014; 76:715.

Summarized and written by myself