Several years ago a longitudinal study of 45 runners and 53 controls (non-runners) over an 18-year period reported that running does not lead to increased incidence of osteoarthritis later in life (see this blog, Aug. 12, 2009).
Now, a much larger study shows that running or even just walking may actually reduce the risk of degenerative diseases such as osteoarthritis. The study examined the number of reported cases of osteoarthritis and hip replacements in over 70,000 runners, as well as walkers and persons who engaged in other exercises of equivalent energy expenditure, over a seven-year period. The authors report that the runners and walkers had fewer reported cases of osteoarthritis and fewer hip replacement surgeries than non-runners who engage in equivalent energy-expenditure exercises.
The decreased risk of osteoarthritis in runners and walkers was strongly associated with the lower BMIs (body mass index) of the runners and walkers. In other words, it may not be the running or walking per se that reduces the osteoarthritis risk. Instead, it may be that running and walking are just very effective ways to keep the weight off, putting less strain on hips and knees.