Running does not destroy your knees. It strengthens them.


Almost every racer, whether veteran or newcomer, short or fast, young or old, shares a bond. Someone will soon warn us that we’re hurting our knees.

“A lot of people think running is bad” for the knees and other joints, said Jean-Francois Esculier, a clinical professor of physical therapy at the University of British Columbia in Kelowna, who studies running.

But the accumulated research, including studies by Esculier and others, generally shows the opposite. In these studies, running does not damage the knees of most runners and, instead, strengthens them, leaving the joints stronger and less damaged than if someone had never practiced the sport.

There are exceptions, though, so it’s important to understand the nuances of science, the unique history of your knees, and the mechanics of what’s really going on behind our kneecaps with every stride we take.

Since the first marathon ended with the death of his entire platoon (composed of a soldier, Pheidippides), some people have been convinced that running must be hard on us, especially on our knees. An online survey conducted by Esculier and his colleagues, its results published this year in the Orthopedic Journal of Sports Medicine, more than half of 2,514 respondents believed that running damages the knees.

This tenacious idea persists despite plenty of evidence to the contrary. Study after study indicates that running rarely causes or exacerbates arthritis in the knees of most runners, even older runners, who are at relatively high risk for arthritis.

Can running strengthen the knees?

Changing public perceptions is difficult, however, said Alister Hart, an orthopedic surgeon and research professor at University College London, who worried about his own knees, especially after completing his first marathon and then limping for decades. days. At this point, he decided, he should dig deeper into the effects of this consuming activity on runners’ joints.

Thus, for a study 2019, he and his orthopedic colleagues recruited 82 middle-aged beginner runners who had entered the 2017 London Marathon. Few of them had done much running, if any, and none were experiencing knee pain. The researchers scanned the runners’ knees before they began a four-month structured training program and, again, two weeks after most had completed the marathon. (Eleven dropped out during practice.)

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Interestingly, although none of the runners reported any knee issues initially, most of their early scans showed signs of incipient joint damage, including cartilage tears and bone marrow damage, which could be the first steps towards arthritis.

But that simmering damage had been partially reversed by training and racing. Two weeks after their first marathon, most of the runners’ existing bone marrow lesions had shrunk, as had much of their frayed cartilage.

But some runners showed symptoms of new, albeit mild, damage to the bone and cartilage just around their kneecaps, a part of the joint that absorbs much of the pounding of running. “We couldn’t ignore this because it probably happened because of training and running,” said Johann Henckel, study co-author and also an orthopedic surgeon at University College London and at the Royal National Orthopedic Hospital. “So we had to ask, is this damage lasting or getting worse?”

If so, running hurt people’s knees.

Scientist-surgeons helped address this concern, however, with a follow-up study, released in 2020, in which they scanned runners’ knees again, six months after their run. Most of them still raced, albeit with reduced mileage.

The new scans showed their knees were healthier now than in the weeks after the marathon. Many lesions and tears that had started to shrink during training were smaller, and the new damage seen around some kneecaps had largely dissipated, with few signs of lesions and tears remaining.

“I feel comfortable at this point saying that running shouldn’t hurt most people’s knees and can, in fact, be beneficial,” Hart said.

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How, however, does running reorganize the knees?

Hart and his colleagues believe that running strengthens the major leg muscles that support the knee, allowing them to take on and offload more of the stresses involved in repeated ground strikes.

The cartilage in the knee is likely swelling too, thanks to the repeated crushing it takes while running, Esculier said. “For a long time it was thought that cartilage couldn’t adapt” to running or other activities, he says, because it lacks blood and nerves. “But the cartilage actually adapts,” he said, “by becoming stronger and more tolerant to compression.”

In a 2022 exam From past MRI studies he co-authored, he and his colleagues found evidence that knee cartilage flattens immediately after a run, but then springs back into shape within hours. With long-term recreational running, he says, the cartilage probably thickens, although that possibility still needs to be investigated.

“Ultimately, the cartilage becomes more robust” with running, Esculier said.

Some runners, however, will develop knee injuries or arthritis. So will many non-runners. A useful line summary of knee and running science, created by Esculier and others, points out that people who are overweight, over the age of 50, with a family history of arthritis or a personal history of knee injuries are at risk significantly higher knee problems than other people they run.

“If running hurts your knees, you don’t have to run,” Hart said. “It’s good to try something else.” He trains with cycling, he says, and his research group studies how cycling affects joints.

But even confirmed skeptics might find stronger knees and other solace in the ride, if they try it. Hart recalls recently presenting his group’s findings on running and knee health to other doctors. One of them, he said, “told me he just didn’t believe it.” But a few weeks later he saw the man jogging in Regent’s Park in London.

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