The minutiae of menisci
There are two menisci in your knee; each rests between the thigh bone (femur) and shin bone (tibia).
The menisci are made of tough cartilage and conform to the surfaces of the bones upon which they rest. One meniscus is on the inside of your knee – this is the medial meniscus. The other meniscus rests on the outside of your knee, the lateral meniscus.
The menisci function to distribute your body weight across the knee joint. Without the meniscus present, the weight of your body would be unevenly applied to the bones in your knee. This uneven weight distribution would cause excessive forces in specific areas of bone leading to early arthritis of knee joint.
The meniscus is C-shaped and has a wedged profile. The wedged profile helps maintain the stability of the joint by keeping the rounded femur surface from sliding off the flat tibial surface. The meniscus is nourished by small blood vessels, but the meniscus also has a large area in the centre of that, with no direct blood. This presents a problem when there is an injury to the meniscus, as without the essential nutrients supplied by blood vessels, healing cannot take place.
The two most common causes of a meniscus injury, or tear, as it is more commonly known, are due to traumatic injury (often seen in athletes) and degenerative processes (seen in older patients who have more brittle cartilage). The most common mechanism of a traumatic meniscus tear occurs when the knee joint is bent and the knee is then twisted.
Individuals who experience a meniscus tear usually experience pain and swelling as their primary symptoms, and there can be painful popping or clicking within the knee joint. Another common complaint is joint locking, or the inability to completely straighten the joint. This is due to a piece of the torn cartilage physically stopping the joint from moving properly.
X-rays and MRIs are the two tests commonly used in patients who have meniscus tears. An x-ray can be used to determine if there is evidence of degenerative or arthritic changes to the knee joint. The MRI is helpful at actually visualizing the meniscus. However, simply ‘seeing’ a torn meniscus on MRI does not mean a specific treatment is needed.
Treatment of a meniscus tear depends on several factors including the type of tear, the activity level of the person with the injury, and the response to simple treatment measures. Often times, if the tear is small the knee will get better with physiotherapy. Exercises to stretch and strengthen the knee are enough to bring it back to normal function. When surgical treatment of a meniscus tear is required, the usual treatment is to trim the torn portion of meniscus, a procedure called a meniscectomy. If you think that you may have a torn meniscus talk to your doctor or a physiotherapist about the proper course of treatment to get your knee back to full health.
Ben Chatterson is a physiotherapist at Rehabilitation in Motion which has four Island locations including two in Campbell River: Willow Point, 923-3773; Quinsam (across from SaveOn Foods), 286-9670; Comox Valley, 334-9670. Ben Chatterson works at the Comox Valley Clinic. Visit www.rehabinmotion.com