Both passivity and hyperactivity can damage knees

Washington: Both high and low levels of physical activities can speed up damage to the knee cartilage among the middle-aged, says a new study. Researchers at the University of California - San Francisco (UCSF) previously had found a link between physical activity and cartilage degeneration. But that study focused on one point in time.

UCSF researchers looked at changes in knee cartilage among a group of middle-aged adults over a four-year period. They used magnetic resonance imaging (MRI)-based T2 relaxation times to track the evolution of early degenerative cartilage changes in the knee, according to an UCSF statement.

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

Researchers analyzed 205 patients, aged 45 to 60 years, from the UCSF-based Osteoarthritis Initiative, a nationwide study funded by the National Institutes of Health on the prevention and treatment of knee osteoarthritis. Participants used a questionnaire to record their physical activity. The researchers measured T2 values of cartilage at the patella, femur and tibia of the right knee joint at baseline and at two- and four-year visits.

According to the results, participating frequently in high-impact activities, such as running, appears linked 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, professor of radiology and chief of musculoskeletal imaging at UCSF.

"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." These findings were presented at the annual meeting of the Radiological Society of North America (RSNA).