"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. "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."The results open up numerous areas for future inquiry, including analysis of the impact of specific types of physical activity on knee cartilage health. For instance, some of the participants in the Osteoarthritis Initiative wore an accelerometer, a device with a motion sensor to record physical activity. "In this study, we used the subjective measure of a questionnaire," Lin said. "The accelerometers provide a more objective way to measure physical activity." Along with the findings on changes in knee cartilage, the study also highlighted the potential of T2 relaxation times as an early indicator of cartilage degeneration. "Standard MRI shows cartilage defects that are irreversible," Dr. Link said. "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." Dr. Link noted that people who have a higher risk for osteoarthritis (such as family history of total joint replacement, obesity, history of knee injury or surgery) can reduce their risk for cartilage degeneration by maintaining a healthy weight and avoiding risky activities and strenuous, high-impact exercise. "Lower impact sports, such as walking or swimming, are likely more beneficial than higher impact sports, such as running or tennis, in individuals at risk for osteoarthritis," he said. Coauthors are Waraporn Srikhum, M.D., Charles E. McCulloch, Ph.D., Michael Neitt, Ph.D., John Lynch, Ph.D., Gabby B. Joseph, Ph.D., and Hamza Alizai, M.D. Note: Copies of RSNA 2012 news releases and electronic images will be available online at RSNA.org/press12 beginning Monday, Nov. 26. RSNA is an association of more than 50,000 radiologists, radiation oncologists, medical physicists and related scientists, promoting excellence in patient care and health care delivery through education, research and technologic innovation. The Society is based in Oak Brook, Ill. ( RSNA.org) Editor's note: The data in these releases may differ from those in the published abstract and those actually presented at the meeting, as researchers continue to update their data right up until the meeting. To ensure you are using the most up-to-date information, please call the RSNA Newsroom at 1-312-949-3233.