By Elizabeth Freedman
Researchers funded by the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) have found that knee malalignment is a key risk factor in the progression of knee osteoarthritis (OA), a degenerative joint disease that is a major cause of disability in people 65 and over.
The alignment of the hip, knee, and ankle influences how the knee responds to loads, and a knee turned inward or outward is subject to additional stress. Participants in the Mechanical Factors in Arthritis of the Knee (MAK) study with more severe malalignment when the study began showed greater decline in physical function after an 18-month period, according to Northwestern University investigator Leena Sharma, M.D., and her colleagues. The scientists also found that more severe malalignment was associated with greater subsequent loss of knee joint space. Bow-legged knee alignment was associated with a significantly greater chance of OA progression in the inner side of the knee, while knock-kneed alignment increased the chance of OA progression on the outer side of the knee.
According to the authors, the MAK study is the first of its kind to demonstrate knee alignment as a factor in the progression of knee osteoarthritis over an 18-month period. It suggests a potential benefit of future interventions to reduce stress caused by knee malalignment.
The risk of disability attributable to knee OA alone is greater than that due to any other medical condition in people age 65 and over. As the U.S. population swells with graying baby boomers, vast numbers of people will experience pain and decreased function associated with osteoarthritis. Today, 35 million people--13 percent of the U.S. population--are 65 and older, and more than half of them have evidence of osteoarthritis in at least one joint. By 2030, 20 percent of Americans (about 70 million) will have passed their 65th birthday, and will be at risk for OA.
Sharma L, Song J, Felson D, Cahue S, Shamiyeh E, Dunlop D. The role of knee alignment in disease progression and functional decline in knee osteoarthritis. JAMA 2001;286(2):188-95.