Dislocation of the knee: an epidemic in waiting?

Knee dislocation is an uncommon but serious injury that has traditionally been associated with high velocity injuries such as motor vehicle accidents. More recently, individual cases of obese individuals sustaining knee dislocation from a low velocity mechanism have been noted. Associated injuries of knee dislocation are common and include popliteal vessel damage requiring surgical repair and injuries to the peroneal nerve. Prompt diagnosis and reduction is essential to reduce the risk of these complications.

We aim to highlight the importance of prompt diagnosis and management of obese patients presenting with knee pain after a seemingly innocuous injury who may have a knee dislocation.

We present a series of four cases of dislocation of the knee that have presented to our hospital over the course of 1 year. Each was sustained by a morbidly obese female of body mass index range 35-41, age range 33-52 years, experiencing a simple mechanical fall from standing. Magnetic resonance image scanning revealed multiple knee ligament rupture in all four cases. One case had peroneal nerve palsy.

This is the first series of such injuries that we are aware of and highlights a potential future increase in incidence of these major injuries as body mass in society increases, placing more strain on health care resources. Practitioners in the Emergency Department need to be aware that serious injury can be present in morbidly obese patients that have sustained no more than a fall from standing height. Prompt investigation and management is essential.