Within the normal knee joint are two C- shaped discs of cartilage called the medial and lateral menisci. They have a unique wedged kidney shape, and a blood supply only to their outer third which decreases as you age. Almost 70% of each meniscus is made up of water. These unique properties allow the knee to function as well as it does but they are also the reason why meniscus tears are one of the most common knee joint injuries.
The wedge shape of your meniscus as- sists with the rotational stability that is created by the anterior cruciate ligament especially during pivoting movements. The large water content allows them act like a shock absorber. As you walk, jump or run the knee absorbs large forces with the amount of force increasing exponentially as the speed of movement increases. Your meniscus helps to disperse these compressive forces over the whole knee therefore minimizing the damage to the cartilage that lines the bone surfaces.
Meniscal tears are often classified as either traumatic or degenerative. In the younger population, meniscus tears are usually due to trauma by twisting on a slightly bent knee. The traumatic type of meniscal injuries is most often sports re- lated. Commonly there is pain and a ‘pop’ is heard. The knee joint swells and occa- sionally the athlete will report a locking or painful clicking sensation. Degenerative tears occur in the older population due to natural age-related degeneration and often the person is unaware of the cause of pain and swelling.
Stay tuned for my next column which will address the management and rehabilitation for the torn meniscus.
Linda Reilly