Dislocation of the knee: imaging findings.

Dislocations of the knee are relatively uncommon injuries. However, the incidence of this injury appears to be increasing. Knee dislocations are most often high velocity blunt injuries, with motor vehicle accidents being a frequent etiology. Other causes include falls from height, athletic injuries, farming and industrial accidents, and even low velocity mechanisms such as a misstep into a hole. Likewise, minor trauma in the morbidly obese is increasingly recognized as a mechanism of knee dislocation. Multiple forms of dislocation exist, with the common factor being disruption of the tibiofemoral articulation. Dislocation can occur in a variety of directions depending on the mechanism of injury. The most common dislocation is anterior, which may be seen in hyperextension injuries such as martial arts kicking. The "dashboard injury" of motor vehicle accidents can result in a posterior dislocation of the knee. Lateral and rotary dislocations are less common. Knee dislocation is more commonly diagnosed in men, with a mean age of 23 to 31 years old. This is the very patient population encountered by Special Operations Forces (SOF) healthcare providers. Given the mechanisms of injury noted above, it is reasonable to conclude that knee dislocations may be seen in a young, active SOF patient population, particularly those engaged in parachuting, fast-roping/rappelling, driving at high speeds during military operations, and mixed martial arts.