Osteoarthritis is the most common form of arthritis, and it is commonly held that regular participation in sports can increase the risk of developing the condition. A new study from Stanford University reveals that, contrary to popular opinion, distance runners are not necessarily prone to degenerating knees. While other sports, such as soccer and weight lifting, are strongly associated with arthritis of the knee, runners seem to experience something very different.
In the study, researchers followed 45 long-time distance runners for almost 20 years, beginning in 1984. At this time most were middle-aged, in their 50s and 60s, and 6.7 percent of them had arthritic knees. An age-matched control group of 53 participants did not have any knee problems. Twenty years later, the runners' knees were in better condition than before. About 20 percent had developed some arthritis, while 32 percent of the control group's knees developed arthritis. And while 10 percent of the control group developed severe arthritis, only 2 percent of the runners did. "We were quite surprised," says Eliza Chakravarty, an assistant professor at the Stanford University School of Medicine and lead author of the study. "Our hypothesis going in had been that runners, because of the repetitive pounding, would develop more frequent and more severe arthritis."
The participants' disability was measured using the Health Assessment Questionnaire Disability Index (HAQ-DI), in which each person self-reported their functional abilities in eight different areas. All participants had radiographic images of the knees taken at the beginning of the study in 1984 and again in 2002. In addition to the lack of association between running and osteoarthritis, the results showed that those with osteoarthritis also had higher body mass index and greater knee damage at the outset of the study. No association was found between knee arthritis and gender, education, previous injury history, or time spent running.
The researchers speculate that running may actually be protective against arthritis. Running conditions your knees to the load, and as long as injuries are avoided, the knees can maintain their top condition throughout the life of the runner. Injuries, however, shift the loading mechanisms and throw off alignment, opening the door to degeneration and arthritis.