Knee Dislocation is a topic covered in the 5-Minute Emergency Consult.

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Basics

Description

  • Defined by the position of the tibia in relation to the distal femur:
    • Anterior dislocation:
      • Most common dislocation, accounts for 60%
      • Hyperextension of the knee
      • Rupture of the posterior capsule at 30°
      • Rupture of the posterior cruciate ligament (PCL) and popliteal artery (PA) occurs at 50°
    • Posterior dislocation:
      • Direct blow to the anterior tibia with the knee flexed at 90°, “dashboard injury”
      • Anterior cruciate ligament (ACL) is usually spared.
    • Medial dislocation:
      • Varus stress causing tear to the ACL, PCL, and lateral collateral ligament (LCL)
    • Lateral dislocation:
      • Valgus stress causing tear to the ACL, PCL, and medial collateral ligament (MCL)
  • Associated injuries:
    • PA injury:
      • Occurs in 35% of dislocations.
      • Anterior dislocations place traction on PA and cause contusion or intimal injury, which may result in delayed thrombosis.
      • Posterior dislocations cause direct intimal fracture and transection of the artery with immediate thrombosis.
    • Peroneal nerve injury:
      • Less common than PA injury
      • If present, must rule out concomitant arterial insult
      • Medial dislocation causes injury by traction of the nerve.
      • Rotary injuries have a high incidence of traction and transection.

Etiology

High-energy injuries such as motor vehicle crashes, auto–pedestrian accidents, and athletic injuries (football most common)

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Citation

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TY - ELEC T1 - Knee Dislocation ID - 307064 Y1 - 2016 PB - 5-Minute Emergency Consult UR - https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307064/all/Knee_Dislocation ER -