My elderly father fell last week and dislocated his knee. Given Dad’s age and general health status (poor), the surgeon doesn’t want to do surgery unless it’s absolutely necessary. I can’t quite figure out why we have to keep taking Dad in for tests and more tests. If they aren’t going to do surgery, what’s the point?

Knee dislocations are known to cause severe ligament damage with knee joint instability. If the blood vessels and local nerves in the area are damaged, the risk of losing the leg is much higher. Such damage can occur even with a single ligament rupture in the knee. And what appears to be minor trauma (e.g., fall from standing) can also cause serious damage to the blood vessels. Without early diagnosis and treatment, loss of limb is a definite possibility.

To prevent this from happening, a careful assessment is made. The surgeon begins with a patient interview, clinical tests, and imaging studies. X-rays can help show any fractures that might be present. A neurologic exam can reveal nerve damage. A quick screen for pulses can help identify vascular (blood vessel) injury. This test should be done before and after any treatment to reduce a dislocated knee. Damage to even small blood vessels can result in local hemorrhaging and loss of vital blood supply.

Testing pulses is a very accurate clinical test. Pulses must be checked every two hours for up to 48 hours. More specific vascular studies (arterial-pressure index, Doppler ultrasound, arteriography) can be ordered if there is any sign of vascular compromise. Restoring circulation quickly (within six to eight hours) is absolutely vital in saving the leg. Most experts agree that treatment for known or suspected vascular injury should not be delayed by doing additional imaging studies.

Other injuries such as disruption of the peroneal nerve or tibial nerve may be present with knee dislocation. The force of the injury is enough to cause traction or stretching to the nerve(s). Anyone with avulsion fracture of the fibula (smaller bone in the lower leg) is at increased risk for peroneal nerve damage.

The surgeon must look for such injuries and address them in treatment. Even with treatment, the risk of sensory and motor damage is high. Difficulty walking because of a foot drop can lead to permanent disability.

With all of these injuries, the patient must be followed carefully. It can take some time before the extent of recovery can be determined. Surgery to restore blood flow involves repairing the damaged blood vessels. Once the blood supply has been restored, then the ligaments may be repaired. This may be done in the same procedure, but more often, the surgeon waits two to six weeks. This gives time for healing of the blood vessel(s). Without adequate blood supply, repairing or reconstructing the ligament won’t be successful.