Knee > Knee Dislocation

What is a Knee Dislocation?

A knee dislocation is an emergency medical situation that can potentially damage any or all of the structures in your knee. The shinbone, kneecap, and thighbone are knocked out of their normal positions by a direct, traumatic force. Depending on which direction the bones move, the surrounding ligaments, tendons, or cartilage may be ruptured or strained. The blood supply or nerve connections to your lower leg also may be damaged. Because it is difficult to tell which knee dislocations have damaged major arteries or veins running through the knee, all knee dislocations should be treated as emergencies. If you suspect a knee dislocation, an ambulance should be called immediately.

Knee dislocations can generally be divided into four categories, depending on the forces that caused the shinbone to move out of joint in relation to the thighbone.

   Hyperextension, or the knee bending in the wrong direction, can move the shinbone forward.

   A direct blow to the front of the shinbone can move the shinbone backwards.

   Twisting forces can rotate the shinbone out of position.

   Impact to the outside or inside of the knee can move the shinbone to the side.

Most people's knees are stable enough to withstand a large amount of strain. High-energy collisions, like those seen in contact sports or in other traumatic accidents, are usually required to cause a knee dislocation. Sports like skiing, football, and ice hockey put athletes most at risk of knee dislocations. Less force can also cause knee dislocations if you have a history of knee weakness. Previous knee injuries, weak leg muscles, or poor joint alignment may put you at risk for a knee dislocation.

A diagnosis of knee dislocation must be made by a trained physician before any treatment will be rendered. The ambulance will drop you off at the emergency room, where you usually are taken to a room where someone on the health care staff should recognize the dislocation and take you immediately to a physician. Most people are given narcotic painkillers as soon as they have been moved to an area where a physician can begin evaluating the injury.

Knee dislocations require immediate treatment. You could be at risk for limb loss if damaged arteries or veins are not treated within six to eight hours after the injury. Physicians generally suggest an ambulance be called to transport someone with a dislocated knee to the hospital's emergency room. If you or someone you know dislocates a knee, the following first aid tips can help you better understand what to do:

   Immediately call for an ambulance.

   Do not attempt to move the injured knee or the injured person unless someone is present who knows how to properly immobilize the knee.

   Try to prevent shock by keeping the injured person still and calm, lying flat on his back. Cover the injured person with a blanket.

   Some dislocations may cause open wounds. Prevent infection by covering the wound. Sterile dressings like gauze are the best option. Physicians recommend covering an open wound with a clean blanket or towel if no sterile dressings are available and letting the paramedics deal with it from there.

   If possible, do not let injured people eat or drink. They may be going under anesthesia soon. The paramedics can give someone an IV if they need fluids, so avoid giving the injured person anything by mouth.

Paramedics will most likely immobilize your leg and place you securely onto a gurney in the back of the ambulance. If possible, it is a good idea to have someone accompany you to the hospital to assist you. Most dislocated knees feel as though they desperately need to be popped back into place. However, paramedics generally do not treat you before arrival at the emergency room because there could be complications that should be treated in the hospital.

In general, the emergency room physician makes a thorough physical exam while deciding the best way to put the joint back in place (reduction). You may need to see an orthopedic surgeon or a vascular surgeon for further treatment of your dislocated knee. To test the integrity of ligaments and tendons in your knee, a physician will touch or gently push the joint to see if the shinbone moves too easily in any direction. The emergency room physician usually feels around your ankle and foot to check for a pulse in your lower leg. The physician may order X-rays before putting your joint back in place. Because a knee dislocation is a very serious injury, it should be evaluated by an orthopedic surgeon. After an appropriate evaluation, the joint will be reduced, or put back into place. This is always done by a physician, usually an orthopedic surgeon. Further evaluation is then undertaken to determine the extent of artery and nerve damage. Many physicians require patients to undergo an arteriogram, which provides images of the arteries and veins running through the knee. Arteriograms take between ten and 15 minutes and can be performed in the ER, the operating room, or in an area reserved for image tests called the angiography area. If you have damaged blood vessels, a vascular surgeon will be consulted to restore normal blood flow through your leg. It is imperative that vascular treatment is rendered as quickly as possible.

Considerations

When treated promptly, 60 to 70 percent of dislocated knees return to full strength. Unfortunately, of the remaining 30 to 40 percent, about half will be at high risk for future dislocations or other problems like arthritis, stiffness, or weakness. To help ensure proper healing, it is critical to receive treatment as soon as possible. The future health of your leg may depend on the duration of time that the knee is dislocated.