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