Runners shown to elude knee arthritis

Gretchen Reynolds / New York Times News Service /

One of the most entrenched beliefs about running, at least among nonrunners, is that it causes arthritis and ruins knees. But a new study finds that this idea is a myth and distance running is unlikely to contribute to the development of arthritis, precisely and paradoxically because it involves so much running.

It’s easy to understand, of course, why running is thought to harm the knee joint, since with every stride, ballistic forces move through a runner’s knee. Common sense would suggest that repeatedly applying such loads to a joint should eventually degrade its protective cartilage, leading to arthritis.

But many of the available, long-term studies of runners show that, as long as knees are healthy to start with, running does not substantially increase the risk of developing arthritis, even if someone jogs into middle age and beyond. A large cross-sectional study of almost 75,000 runners published in July, for instance, found “no evidence that running increases the risk of osteoarthritis, including participation in marathons.” The runners in the study, in fact, had less overall risk of developing arthritis than people who were less active.

But how running can combine high impacts with a low risk for arthritis has been mysterious. So for a new study, researchers at Queen’s University in Ontario and other institutions looked more closely at what happens, biomechanically, when we run and how those actions compare with walking.

Walking is widely considered a low-impact activity, and many doctors recommend it for older patients, to mitigate weight gain and stave off creaky knees.

But before the new study, which was published last month in Medicine & Science in Sports & Exercise, scientists had not directly compared the loads applied to people’s knees during running and walking over a given distance.

To do so, the researchers recruited 14 healthy adult recreational runners, half of them women, with no history of knee problems. They taped reflective markers to the volunteers’ arms and legs for motion capture purposes, and asked them to remove their shoes and walk five times at a comfortable pace along a runway approximately 50 feet long. The volunteers likewise ran along the same course five times at about their usual training pace.

The researchers used the runway data to determine how much force the men and women created while walking and running, as well as how often that force occurred and for how long.