knee dislocation disaster

Tuesday, August 30, 2016

While most injuries require some sort of significant trauma, bad luck may be the most ominous cause of disaster. Bad luck has befallen Vikings quarterback Teddy Bridgewater, who dislocated his knee without being touched. Normally, this injury requires high velocity and high impact because the knee joint is held stable by four ligaments in addition to the quadriceps and hamstring muscles.

knee dislocation anterior knee dislocation

Anterior Dislocation                              Posterior Dislocation

Knee dislocations are a big deal and should not be confused with kneecap (patella) dislocations, which are relatively common, affect women more than men because of anatomic and muscle attachment differences and are easily taken care of in the field or the ER. Knee dislocations, though, not only tear ligaments but also potentially tear the popliteal artery that supplies blood to the lower leg.

It is drilled into emergency doctors that a knee dislocation is an injury that can be missed, because the knee can relocate spontaneously before medical care happens. That can lull doctors into a false sense of security but that may lead to disaster. A missed diagnosis may lead to leg amputation if there is a damaged popliteal artery. For that reason, in addition to the orthopedic surgeon, a vascular surgeon usually gets involved in the evaluation and treatment of this injury.

Once the dislocation diagnosis is made, the next step is to evaluate the artery. There are different diagnosis options, whether it is repeatedly measuring blood pressures in the arms and legs (ankle-brachial index) or performing CT angiograms, the index of suspicion for artery injury needs to be very high. And that suspicion needs to be maintained for a few days, just in case there is delayed clotting in the artery.

Not every dislocation is the same. The four ligaments that hold the knee stable can be torn in different combinations depending upon the forces placed on the knee and the direction it dislocates. Regardless, the surgery to repair the ligament damage needs to happen within a few days of injury

This is not an injury that always gets better, even with the best of care. The prognosis for a “normal” knee, one which is stable and without pain happens about 60-70% of the time, 20% will have reasonable function and the last 20% will have a chronically painful, unstable knee.

Knee dislocation is the same injury that derailed the career of Robert Edwards in 1998. He was playing in an NFL flag football game as part of that year’s Pro Bowl events when he was injured. It took four years for him to rehab and return to play one season in the NFL and four more in the CFL.

It seems though that the only good news for Mr. Bridgewater comes from the Minnesota Vikings press release: “Fortunately, there appears to be no nerve or arterial damage”.

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