Posterior Cruciate Ligament Injury

We're in ski season and so a few unfortunate individuals will suffer few knee injuries. A while back, a reader asked me to describe an uncommon injury, which is a torn posterior cruciate ligament (PCL).

This injury usually occurs during a fall. As you can see from the drawing, the PCL keeps the lower leg bone (tibia) from moving too far back in relation to the upper leg bone (femur). If a sudden unnatural force is applied, usually a direct blow to the front of the lower leg near the knee while the knee is bent, the tibia is jammed backwards and the PCL may be torn. In the skiing situation, this usually happens during a fall and a tumble, when someone strikes an immovable object, or when the knee is bent or "twisted" and struck forcefully from the side.

The immediate sensation is pain, and there may be a feeling of instability to the knee, particularly when trying to walk or change levels (e.g., walk over the snowpack or on stairs). When the injury occurs, there usually is not the "pop" sensation noted with an anterior cruciate ligament tear. However, the knee will almost always swell, because there is bleeding into the knee joint and/or soft tissue swelling.

The diagnosis may be surmised by taking a good history and understanding the mechanism of injury, performing a physical examination to determine what elicits pain and instability (commonly, the "posterior drawer test"), and these days, most often by magnetic resonance imaging (MRI). Sometimes an x-ray is taken prior to the MRI to determine whether or not there is a broken bone, but the x-ray does not show the structure and integrity of the ligaments and cartilage within the knee.

Until you can see your doctor, you should apply ice packs a few times a day for 15 minutes to help diminish pain and swelling, and avoid weight bearing. Use crutches if you have them. A broadly-applied (mid calf to mid thigh) pressure wrap may help diminish pain and increase stability, but take care to not apply it too tightly. If you decide to take pain medication, avoid aspirin-containing products (to diminish bleeding). If you have a knee brace (usually from a previous injury or as a preventative appliance for certain sports, wear it to provide extra stability.

Whether or not you will need surgery depends on the magnitude of the tear and the degree to which you respond to rehabilitation. Small tears are sometimes treated "conservatively" without surgery and can be rehabilitated under the guidance of an experienced physical therapist. If the knee does not improve or if the tear is sufficiently extensive initially, surgery may be recommended to replace the PCL with a graft.

drawing courtesy of www.zimmer.co.nz