In an article published in March 2007, a team of scientists presented their result on the relationship between self-reported recreational exercise and the development of knee osteoarthritis (OA). This team was lead by Dr. David T. Felson, M.D., M.P.H of Boston University, and the article was published in Arthritis Care & Research.

Exercise has long though to decrease the risk of developing knee OA via healthy effects on cartilage and muscle strengthening. At the same time, however, some evidence suggests that exercise may also predispose to knee OA via joint loading and the potential for traumatic injury.

To help determine which is the case, Felson et al gave a group of 1,279 subjects, who were of the average age of 53 and thought to be genetically predisposed to osteoarthritis, a series of knee radiography tests in addition to asking them questions about their habitual exercise habits. Regular walking for exercise was reported in 48% of subjects. Knee radiography was then repeated 1 to 2 years later when subjects were asked questions about interim knee injury.

It was found that 26% of subjects reported knee pain at baseline at the interim, while only 9.5% knees studied developed incident knee OA. Most knees with incident knee OA were symptomatic and most showed OA in the tibiofemoral compartment. No difference was found in incident OA for those walking more or less than 6 miles per week compared to those reporting no regular walking for exercise. And although a small percentage of subjects reported regular jogging or running, there was not a significant risk or protective effect associated with these activities.

The team concluded then that self-reported habitual physical activity was not associated, either positively or negatively, knee OA.