Two fibro-cartilaginous crescents, the menisci serve as cushions against joint cartilage degradation where the knee connects with the shin and thigh bones. Loss of meniscal function is recognized as a strong risk factor for knee osteoarthritis (OA). In the United States, about 6 percent of the over 30 through middle-age population and between 11 and 15 percent of senior citizens, age 65 and up, suffer from knee OA in form of frequent knee pain, aching, or stiffness. The prevalence of this routinely aggravating, often disabling condition is increasing. Associated with the toll of aging and obesity, as well as sports injuries, tears to the menisci are a common finding on magnetic resonance images, especially in the OA knee. However, whether meniscal damage foreshadows the development of knee pain in middle aged or elderly or directly causes it remains unknown.
Toward their goal of improving the early detection of knee OA, researchers with the Multicenter Osteoarthritis (MOST) Study set out to evaluate the effect of meniscal damage on the development of knee pain, aching, or stiffness in middle-aged and older adults. Based on their findings, featured in the December 2007 issue of Arthritis & Rheumatism (http://www.interscience.wiley.com/journal/arthritis), meniscal damage does often not directly provoke knee symptoms. Any association between meniscal damage and frequent knee pain seems to be present because both pain and meniscal damage are related to OA, notes study spokesperson Dr. Martin Englund of Boston University School of Medicine, and not because of a direct link between the two.
Researchers began by focusing on 3,026 individuals between the ages of 50 and 79, who either had signs of knee OA or were at a high risk of developing it. Recruited from two U.S. communities Birmingham, Alabama, and Iowa, City participants included men and women, whites and ethnic minorities. Based on telephone interviews and clinical visits with members of the study population, 110 case knees were identified. They were defined as knees free from symptoms at baseline, which had developed frequent pain, aching, or stiffness at the studys 15-month culmination mark. 220 control knees were drawn randomly from those knees with no frequent symptoms at baseline that did not become cases.
Magnetic resonance imaging (MRI), trusted for its high sensitivity to detecting tissue and cartilage changes, was performed on case and control knees at baseline and at 15 months. Then, 2 musculoskeletal radiologists blinded to the case-control status of its subject assessed each film for meniscal damage using the following scale: 0 = intact, 1 = minor tear, 2 = non-displaced tear or surgical repair, and 3 = displaced tear, resection, maceration, or destruction. Finally, the effect of meniscal damage on the development of frequent knee pain, aching, or stiffness was analyzed by contingency tables and logistic regression.
At baseline, meniscal damage was detected on 38 percent of case knees and 29 percent of control knees. As expected, meniscal damage was more frequent in knees in which previous surgery or serious injury had been reported. Although there was a modest association between meniscal damage score and the development of frequent knee pain, aching, and stiffness after adjusting for age, sex, and body mass index meniscal damage was mostly present and pronounced in knees with radiographic evidence of OA.
When considering the co-occurrence of OA and performing a stratified analysis, researchers found no independent association between meniscal damage and the development of frequent knee symptoms. Meniscal damage in older adults is highly associated with OA of the knee, Dr. Englund makes clear. However, meniscal damage often seems not to be directly responsible for later symptoms, while other features of OA may be so. Stressing the importance of treating OA as a whole-joint disorder, this study calls attention to the risk of misinterpreting meniscal damage as the direct cause of knee pain. As Dr. Englund acknowledges, it also emphasizes the need for further research into the possible role of different types and sites of meniscal damage in contributing to knee pain.
|Contact: Amy Molnar|