Knee (tibiofemoral) dislocations

[Kit]

Knee dislocations are commonly accompanied by arterial or nerve injuries. Knee dislocations threaten limb viability. These dislocations may spontaneously reduce before medical evaluation. Diagnosis is usually by x-ray. Vascular and neurologic evaluation is required; vascular injury is identified by CT angiography. Immediate treatment is closed reduction and treatment of vascular injuries.
(See Overview of Dislocations.)
Most anterior knee dislocations result from hyperextension; most posterior knee dislocations result from a posteriorly directed force to the proximal tibia while the knee is slightly flexed. Most knee dislocations result from severe trauma (eg, in high-speed motor vehicle crashes), but seemingly slight trauma, such as stepping in a hole and twisting the knee, can sometimes dislocate the knee, with vascular and neurologic complications, particularly in morbidly obese patients (1).
Knee dislocations always damage

Structures that support the knee joint, causing joint instability

Joint instability due to extensive ligament injury is a common long-term complication of knee injury.
Other structures that are commonly injured include the

Popliteal artery (particularly in anterior dislocations)
Peroneal and tibial nerves

Popliteal artery injury may initially affect only the intima and thus does not cause distal limb ischemia until the artery later becomes occluded. Undiagnosed arterial injury has a high risk of ischemic complications, which may lead to amputation.