Cartilage loss is a major component of osteoarthritis (OA), a joint disease that affects over 20 million Americans. In knee OA, cartilage loss is influenced by knee injury, as well as obesity and age. Every healthy knee is supported and protected by a pair of meniscus.
This C-shaped tissue has many functions in the knee, including load bearing, shock absorption, and stability enhancement. The onset of knee OA after meniscectomy, the surgical removal of all or part of a torn meniscus, is fairly common and traditionally considered a result of the joint injury that leads to the operation in the first place.
While meniscectomy appears to be a significant risk factor for OA, researchers know little about the effect of meniscal damage and abnormalities on cartilage loss in knees with a predisposition for the disease. The March 2006 issue of Arthritis & Rheumatism shares the results of a study that sheds new light on the importance of an intact and functioning meniscus for patients with symptomatic knee OA.
The study, led by David Hunter of Boston University School of Medicine, focused on 257 subjects enrolled in the Boston Osteoarthritis of the Knee Study. The majority, 58 percent, were men and the mean age was 66.6 years. All subjects met the American College of Rheumatology criteria for symptomatic knee OA, confirmed by X-rays and self-reports of frequent knee pain and stiffness. At the study's onset and follow-up examinations at 15 and 30 months, participants underwent magnetic resonance imaging (MRI) of the more symptomatic knee. Using the MR images, researchers measured the position of the meniscus, as well as evaluated and scored the severity of meniscal damage. Among the MRI-assessed knees, 29% had a previous injury, 27% had a previous surgery, and 5% had a previous meniscectomy.
The researchers, as expected, found a high correlation between meniscal malposition and meniscal damage. The impact of meniscal abnormality on cartilage lost was most pronounced in the medial tibiofemoral joint--the inner joint connecting the knee to the lower leg. Each measure of meniscal misalignment was associated with an increased risk of cartilage loss. There was also a strong association of meniscal tears with cartilage loss. Reductions in the coverage and height of the meniscus, provoked by partial dislocation of the meniscus, also increased the risk of cartilage loss.
This study does not distinguish the type of meniscal tear that may propel cartilage loss or implicate meniscus damage as a cause of OA. However, it does call attention to the potential of a strong, whole meniscus to protect the knee from rapid devastation in the early stages of OA, and perhaps even mitigate the need for need replacement surgery. "At present, efforts are being made to preserve a damaged meniscus rather than remove it, and an industry of meniscal replacement is developing," Dr. Hunter notes. "Our study points to the need for critical, prospective evaluation of these new therapeutic options."