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. 

Researchers analyzed 205 patients, aged 45 to 60 years, from the UCSF-based Osteoarthritis Initiative, a nation-wide study funded by the National Institutes of Health on the prevention and treatment of knee osteoarthritis.