On the one hand, it would make sense that pounding the pavement for lots of miles each week could take a toll on the knees—namely in the form of osteoarthritis, the most common type of arthritis. On the other hand, runners tend to stay lean, and that could take pressure off the knees and ward off cartilage breakdown.
A team of VA and university researchers has cut through the conundrum with hard data from a study of more than 2,000 people. The verdict? Runners are at no increased risk for symptomatic knee osteoarthritis.
The findings appeared online June 22, 2016, in the journal Arthritis Care and Research.
Nearly 30 percent of study group identified as runners
The researchers were led by Dr. Grace Lo of Baylor College of Medicine and the VA Center for Innovations in Quality, Effectiveness and Safety, in Houston. They analyzed data on 2,637 people who had taken part in a larger study called the Osteoarthritis Initiative, funded by the National Institutes of Health and partners from the pharmaceutical industry. The average age of the group was about 64. Nearly 56 percent were women.
"Running does not appear detrimental for knee health."
Nearly 30 percent of these study volunteers reported being a runner during at least one period in their adolescent or adult life.
The team found no evidence of increased risk of knee pain, or X-ray evidence of osteoarthritis, or a combination of the two, among runners, compared with those who had never engaged in leisure running for exercise.
"Running does not appear detrimental for knee health,"wrote Lo and her colleagues.
They caution, though, that because of how the study was designed, the conclusion applies only to those without pre-existing arthritis.
"Among those without osteoarthritis,"they wrote, "running should not be discouraged for a concern of an increased risk for developing knee osteoarthritis or associated frequent knee pain."
Study not designed to show cause and effect
Runners may have even fared a bit better than non-runners in the study. Any history of running was associated with lower odds of osteoarthritis and frequent knee pain, compared with no history of running.
But interpreting the findings is tricky. Since the study was observational and wasn't designed to show cause and effect, the researchers can only speculate about the possible mechanisms involved.
For example, it could be that running somehow helps to prevent knee arthritis—perhaps by keeping people trim. Lower body weight mean less stress on the knees, in general. Lo's team theorizes that running might also exert other biomechanical effects on the knees that help keep arthritis in check.
Another possible interpretation is that runners tend to have healthier lifestyles overall. They might be more likely to eat wisely, or to not smoke. Such factors could lower the risk for arthritis and other chronic diseases, and perhaps even help counter any potential harm from the mechanical load that running puts on the knees.
In theory, a better way to tease out the precise relationship between running and knee health would be to follow runners versus non-runners over time. Ideally, the two groups would be roughly similar in most other parameters: demographics, lifestyle, other exercise habits, overall health. But such a study would require many years and would therefore be difficult to conduct, says Lo.
Pending further clarity from more research, the findings from Lo's group are being hailed by many runners as reassuring news.
One major strength of the study, Lo told Runner's World, was that it used rigorous methods of assessing knee osteoarthritis, based on X-rays and symptom reports.
Another was that, unlike many past studies on running, it focused on average recreational runners, not elite athletes. She told the magazine, "This is the largest study to look at running similar to what the everyday person would do."
Mandatory running, as in military, may shift equation
Lo raises an interesting question, though, about the extent to which the findings may apply to military Veterans. The study included only people who were able to decide on their own whether they wanted to run for leisure, and how much. It could be that people who felt knee pain when they ran simply never took up the activity on a regular basis, whereas those who were more comfortable and enjoyed the activity ended up becoming regular runners.
"This is a very different setting than running in the military, where it is a cornerstone of physical training and is compulsory,"said Lo in an email interview with VA Research Currents. "People in the military don't get to choose whether or not they will run. They do it because they are told to do it. They have to participate even if they have pain and don't feel like running. It's not clear whether running in this setting is harmful or beneficial."