Knee Dislocation


50YO male involved in a RTA. HEMS transport the patient to hospital. You attend the trauma call as the on-call SpR for T+O.


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I would ensure I attend the trauma call urgently. Given the high mechanism of injury the patient requires management as per ATLS guidelines. I would stabilise the C-Spine and perform a primary survey assessing the patients: airway, breathing, circulation and disability. I would treat any life threatening injuries identified.

Following this I would perform a secondary survey. As part of the secondary survey. I would manage the affected limb. I would check the limbs neurovascular status. I would ensure that it is a closed injury and check for a dimple sign (buttonholing of the femoral condyle through the capsule).

I would reduce the affected limb with the assistance of my anaesthetic/A+E colleagues and place the affected limb in an above knee backslab with around 20 degrees of knee flexion. Following this I would recheck/document the neurovascular status of the limb (DP and PT pulses).

If pulses are absent post reduction I would:

  • Confirm the knee is reduced
  • Perform a CT angiogram
  • Contact vascular and theatre teams.

If the pulses are normal I would:

  • Perform an ABPI
    • If the ABPI is >0.9 the patient should be observed as an inpatient for 24 hours.

If the ABPI is <0.9 an urgent CT angiogram should be arranged and discussion with vascular surgery and theatre.

This is a lateral plane film radiograph of a skeletally mature individual, taken on an unknown date of an unknown individual. There is an Posterior knee dislocation. There does not appear to be any associated fractures.

Anterior dislocation (30-50%)

Kennedy classification (Direction of displacement)


–       Intimal tear

–       Highest rate of peroneal nerve injury



–       Highest rate of vascular injury/incidence of complete popliteal tear










Schenck classification (ligamentous injuries)





ACL and PCL + MCL or LCL


ACL and PCL + MCL and PCL (has highest rate of vascular injury)


Multiligament with periarticular fracture



The popliteal artery is fixed at both extremities, at the hiatus of the adductor canal/adductor magnus and at the soleus muscle. Therefore movement is restricted.

  • Floor: poplitus
  • Superior-medial: Semimembranosus
  • Superior-lateral: Biceps femoris
  • Inferior-medial: medial head of gastrocnemius
  • Inferior-lateral: lateral head of gastrocnemius
  • Nerve: common peroneal artery
  • Vein: popliteal vein
  • Artery: popliteal artery
  • Lymph nodes and fat
  • Anterior tibial plateau
  • Medial aspect of lateral femoral condyle

Foot drop (inability to dorsiflex the foot) and loss of sensation of the lateral aspect of the leg and dorsum of the foot).

Superficial peroneal nerve

  • Peroneus longus and brevis
  • Foot eversion

Deep peroneal nerve

  • Tibialis anterior
  • Ext digitorum longus
  • Ext hallucis longus
  • ACL
  • MCL

Meniscal injury (lateral meniscus more commonly injured when ACL ruptures occur)

The patient undergoes a CT angiogram of the lower limb.


A = Popliteal artery

B = Anterior tibial artery

C = Femoral artery

D = Tibioperoneal trunk

E = Peroneal artery

F = Posterior tibial artery