Learning Radiology xray montage

Dislocation of the Knee

General Considerations

  • Uncommon dislocation
  • Most are either anterior or posterior
  • Using the position of the tibia as the reference
    • Anterior dislocations (most frequent)
      • Hyperextension
      • Posterior dislocations (second most frequent)
        • Force to anterior tibia with knee flexed as in MVC or falls
      • Medial, lateral or rotational
        • Valgus, varus or rotational forces
      • As many as 50% of knee dislocations spontaneously self-reduce
    • Can lead to underestimation of damage
  • Most believe that dislocation requires injury to both anterior and posterior cruciate ligaments and either of the collateral ligaments

Clinical Findings

  • Gross deformity
  • Swelling
  • Intense pain

Imaging Findings

  • Conventional radiography is the study of choice
    • MRI will demonstrate ligamentous injuries
  • Fractures of tibial plateau are relatively common
    • Also proximal fibula and tibial spines


  • Immediate closed reduction after full evaluation for associated injuries
  • Surgical repair of ligamentous injuries is usually carried out several weeks after injury


  • Co-existent vascular injuries
    • Popliteal artery
  • Loss of limb
  • Compound fractures are common (30%)
  • Peroneal nerve injury
  • Ligamentous injury
  • Deep vein thrombosis
  • Compartment syndrome


  • High velocity injuries result in more damage and have a worse prognosis than low velocity injuries
  • Most will regain full use of a stable knee

Knee dislocation

Knee Dislocation

Posterior and Lateral Dislocation of Knee. The tibia is displaced laterally and posteriorly relative to the femur (red arrow). The patella is displaced laterally (black and white arrows) and comes to lie over the lateral femoral condyle. Some degree of rotational force is usually required to produce this type of injury.
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Knee Dislocations   eMedicine   Green, J; Shahrdar, C; Owens, B

A Review of Knee Dislocations. Henrichs, A. Journal of Athletic Training 2004;39(4):365–369