Too Much or Too Little Physical Activity May Increase Knee Osteoarthritis Risk

A new study found that both rigorous physical activity and sedentary behavior are associated with early damage to cartilage in the knee that might progress to knee osteoarthritis. (Image: Ken Tannenbaum/

Chicago—Numerous studies have demonstrated the benefits of physical activity in reducing the risk of a variety of health problems, including heart disease and Alzheimer disease. Now, new findings suggest that for at least 1 condition, osteoarthritis of the knee, both sedentary living and rigorous exercise are linked with early degenerative changes in knee cartilage that might lead to osteoarthritis.

The finding was presented during a press conference today at the Radiological Society of North America’s Scientific Assembly and Annual Meeting.

The researchers, from the University of California, San Francisco (UCSF), analyzed magnetic resonance imaging (MRI) studies of 205 patients, aged 45 to 60 years, who were enrolled in the Osteoarthritis Initiative, a National Institutes of Health study on the prevention and treatment of knee osteoarthritis. The study participants were followed up for 4 years and were periodically assessed with MRI-based T2 relaxation times to track the evolution of early degenerative cartilage changes. (There is increased water movement in damaged cartilage, which presents as increased T2 relaxation time.) Using information from a questionnaire given to participants, the researchers divided the enrollees into 3 groups based on their level of physical activity.

The researchers found study participants with the highest activity levels had greater increases in T2 relaxation times compared with those with moderate activity levels. In addition, those with the lowest levels of physical activity also had higher T2 relaxation times. Some amount of movement is necessary to keep the knee properly lubricated, which may explain the relationship between low activity and high T2 times, explained Thomas M. Link, MD, one of the researchers and a professor of radiology at UCSF, suggesting there may be an optimal level of physical activity to preserve the knee cartilage.

The researchers suggested that people at risk of developing osteoarthritis (those who are obese, those who have a history of knee injury or surgery, or those who have a family history of total joint replacement) might want to consider less strenuous forms of exercise, such as walking or swimming, instead of high-impact activities such as running or tennis.

Although assessing MRI-based T2 relaxation times is currently only a tool for research, the researchers said the approach might have a place in the clinical setting. They noted that current diagnostic imaging for osteoarthritis occurs late in the condition’s development, when cartilage defects are irreversible; T2 relaxation times might make it possible to identify cartilage damage earlier, at a time when the degenerative process might be reversed.

Categories: Exercise, Magnetic Resonance Imaging, Osteoarthritis, Radiologic Imaging, Rheumatology