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dislocation of the knee joint

see also:

  • after 8 hours of ischaemia, most will require an above knee amputation!!!
  • urgent reduction is critical!
  • assume all patients have a vascular injury until proven otherwise


  • an important time critical red flag of the acutely injured knee in ED is the possibility of a knee dislocation having occurred (not a patellar dislocation), as this requires urgent investigation to exclude a possible vascular injury to the popliteal vessels and potential
  • knee dislocation is uncommon and mainly occurs with high energy injuries such as motor vehicle accidents, falls from a height, high impact sports, downhill snow skiiing, etc.
  • knee dislocations are an increasingly common complication of gym exercises such as:
    • falling awkwardly when doing hamstring stretches with foot caught on bar
    • leg presses with heavy loads eg. 200kg single leg press
  • most dislocations are clinically evident and require urgent reduction as they may be limb threatening due to vascular injury
  • some spontaneously reduce but there is still potential vascular injury which needs emergent assessment.

potential complications

  • popliteal artery injury
    • after 8 hours of ischaemia, most will require an above knee amputation!!!
    • lesions or thrombosis may not become clinically apparent for several weeks after injury
  • compartment syndrome of the leg
  • common peroneal nerve injury
  • associated injuries include ACL/PCL/meniscal/collateral ligt/tibial plateau fracture/tibial shaft fracture/proximal fibular fracture
  • DVT
  • late onset complications:
    • pseudoaneurysm
    • arthosis
    • stiffness
    • chronic pain

ED management of the dislocated knee

  • an anteromedial skin furrow suggests posterolateral dislocation and these are irreducible by closed reduction methods due to buttonholing of the femoral condyle - these patients need urgent open reduction
  • other dislocations:
    • if good peripheral pulses, consider pre-reduction imaging
    • if peripheral pulses impaired, immediate reduction in ED is indicated to save the limb.

closed reduction in ED

  • care and precautions as per usual ED Mx of conscious sedation
  • two clinicians required to reduce the knee while a third manages airway, sedation, etc
  • one clinician grasps femur, the other the tibia - avoid applying pressure in popliteal fossa as this may exacerbate vascular injury
  • apply longitudinal traction, and most will reduce
  • if unsuccessful, reverse the direction of the dislocation
  • if still unsuccessful, urgent ortho team consult

post-reduction Mx

  • check for signs of vascular injury
  • document popliteal and pedal pulses - but note that presnce of pulses does not exclude injury!
  • consider measuring the ankle-brachial index (ABI)
  • consider urgent doppler USS
  • if any vascular injury present, urgent consult with vascular surgeon
  • post-reduction plain Xrays
  • many advocate routine CT angiography after any knee dislocation given the poor sensitivity of physical examination
  • admit all patients
  • 3-4hrly neurovascular obs for at least 24 hours
  • post-discharge instructions:
    • repeat Xrays within 1 week to confirm still reduced
    • patient to return ASAP if any vascular symptoms
    • close orthopaedic follow up to determine need for and timing of surgical reconstruction of knee joint

features suggestive of a spontaneously reduced knee dislocation

  • presence of a significant posterolateral corner injury which is suggested by either:
    • fibular styloid fracture on lateral Xray (“arcuate sign”) is pathognomic of posterolateral corner injury and note that this is a different fracture to a fibular head fracture
    • Segond avulsion fracture from the tibial condyle on AP Xray is associated with ACL injury and posterolateral corner injury
    • Medial Segond avulsion fracture from the medial tibial condyle on AP Xray is associated with PCL injury and posterolateral corner injury
    • External Rotation Recurvatum Test:
      • The great toes are held by the examiner as both legs are raised simultaneously. A positive test results in hyperextension, external rotation of the tibia, and apparent tibia vara of the affected limb.
    • the Dial Test:
      • This test is performed with the knee flexed at 30deg and 90deg. The patient may be supine or prone.
      • The thighs are stabilized by an assistant or a strap, while the lower legs are synchronously externally rotated.
      • The amount of external rotation at the tibial tuberosity is compared with the other side. If prone, the external rotation may be measured by the thigh-foot angle. An increase of 10 to 15 degrees is considered a positive test and suggests a significant posterolateral corner injury.
knee_dislocation.txt · Last modified: 2014/02/08 22:28 by

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