Opposite extremes of activity spectrum don't benefit patient knees

Knees are needy when it comes to activity. Too much physical vigor can put them out of commission, while too little can leave them in a state just as ravaged.

According to researchers from the University of California in San Francisco (UCSF), both hyper-extensive and hyper-minimal levels of physical activity can promote knee cartilage degeneration in middle-aged adults. Through the use of MRI-based T2 relaxation times, the study’s cohort reflected the evolution of changes in knee cartilage, and thus pinpointed elements of early degenerative cartilage within a given participant’s patella.

"T2 relaxation times generated from MR images allow for analysis of the biochemical and molecular composition of cartilage," said Wilson Lin, B.S., research fellow and medical student at UCSF, in a news release. "There is increased water mobility in damaged cartilage, and increased water mobility results in increased T2 relaxation time."

The study’s subject pool consisted of 205 patients, from age 45 to 60, who were a part of the National Institutes of Health’s Osteoarthritis Initiative — a nationwide study investigating prevention and treatment tactics for knee osteoarthritis. Researchers quantified T2 values of cartilage at the patella, femur and tibia of the right knee joint at baseline and at two- and four-year visits. The results found that those participating in running or other high-impact activities were associated with more degenerated cartilage and potentially a higher risk for development of osteoarthritis.

“When we compared the scores among groups, we found an accelerated progression of T2 relaxation times in those who were the most physically active," said Thomas M. Link, M.D., professor of radiology and chief of musculoskeletal imaging at UCSF, in a new release. "Those who had very low levels of activity also had accelerated progression of T2 values. This suggests that there may be an optimal level of physical activity to preserve the cartilage."

“In this study, we used the subjective measure of a questionnaire," Link continued. “The accelerometers provide a more objective way to measure physical activity. Standard MRI shows cartilage defects that are irreversible. The exciting thing about the new cartilage T2 measurements is that they give us information on a biochemical level, thus potentially detecting changes at an earlier stage when they may still be reversible."

Study findings were presented at the annual meeting of the Radiological Society of North America.

Find patient-friendly information about MRIs of the knee here.

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