Most commonly occur after MVCs but also seen after falls, industrial accidents and sports related trauma.
Up to 50% of knee dislocations will have spontaneously reduced by time of presentation to the ED.
Strongly consider a spontaneously reduced knee dislocation in those with a significant mechanism of injury in the setting of multidirectional instability (3 or more ligaments torn).
A thorough neurovascular examination is a must due to the risk of vascular (34%)(5-79%) and nerve (23%)(16-40%) injuries. There is a must higher incidence of these injuries in high force trauma such as from a MVC. The popliteal artery and common peroneal nerve are at the greatest risk
Though the absence of distal pulses suggests vascular injury, the presence of pulses cannot be used as evidence of the lack of a vascular injury.
After reduction, the knee should be immobilized in 15-20° of flexion in a knee immobilizer.
