PLICA SYNDROME OF THE KNEE
1. What is it?
The knee plica are residual extra folds of synovial tissue. Synovial tissue is the tissue which lines the knee joint. These folds of tissue can become inflamed or scarred if subjected to either repetitive overuse or severe direct trauma. In some cases the plica may even become entrapped in the knee joint itself.
There are 3 plica in the knee, the most significant one being the mediopatellar plica, which is found on the medial side of the knee, somewhat underneath the patella. Of note is that 40% of the population do not have knee plica, as this tissue was completely resorbed during fetal development.
2. What are the causes/predisposing factors of injury?
Repetitive overuse from running, cycling or overstretching can irritate the plica. Direct trauma such as a hard fall on the knee or a dashboard injury where the knee strikes the dash in a car accident can also irritate the plica. Tight hamstrings also seem to be a predisposing factor.
3. What are the symptoms?
Plica syndrome usually presents as knee pain that is worse when sitting with the knee bent, increases as you arise to a standing position then improves as walking continues. The pain is typically felt on the inside aspect of the knee, just above the lower part of the kneecap. Other symptoms such as mild swelling, popping noises, snapping and a catching or locking sensation may occur.
The symptoms of plica syndrome can be quite similar to those of a medial meniscus tear or of chondromalacia. To distinguish these from each other, an arthroscopic examination is recommended.
4. What can be done to prevent or treat this injury?
Prevention would include hamstring flexibility stretches and quadriceps strengthening exercises. However, quadriceps strengthening exercises should be limited to the last 5 to 10 degrees of motion, since compression of the kneecap is greater when the knee is at 90 degrees. Strengthening of the hip adductors is also recommended.
Treatment can be via cross friction massage, ultrasound, ice or laser. I prefer to use ultrasound first, possibly with a topical anti-inflammatory, and then do cross friction massage. The ultrasound makes the tissue more pliable for the cross friction massage and is generally less sore afterwards.