​Here’s What Running Really Does To Your Knees

It’s one of the most common refrains in the fitness world: Running will wreck your knees. But how true is it, really?

Researchers from Spain tackled that age-old question. After crunching the numbers from 17 studies including over 125,000 people, they concluded that recreational running doesn’t seem to put your joints at risk.

They key word, though, seems to be recreational. Just under 4 percent of recreational runners—those who run in an amateur context—developed hip or knee arthritis, compared to just over 10 percent of sedentary people who didn’t run at all. But when looking at competitive runners, or those at an elite level who take part in pro or international competitions? Over 13 percent of them had hip or knee arthritis.

In fact, recreational runners were 14 percent less likely to develop hip or knee arthritis than sedentary people were. On the flip side, competitive runners were 34 percent more likely to get an arthritis diagnosis than those who stayed parked on their butts.

These relationships held true in people who ran for up to 15 years—there just wasn’t enough studies done on running longer-term to draw firm conclusions for that, the researchers say.

In animal trials, slight or moderate running—as gauged by distance—has been shown to have a chondroprotective effect, meaning it delays the progressive joint space narrowing that you see with arthritis. But this protection wasn’t seen in longer, more intense distances, according to the researchers.

Because this study didn’t look at mileage, it can’t say for sure what distance is considered safe or protective for you knees and hips.

Bottom line? You don’t have to worry that running for fun will hurt your knees—recreational running may even protect them.

Still, there are some things you can be doing that put your joints at risk.

This article originally appeared on menshealth.com.