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Even after 1,000 marathons, running isn’t bad for your knees

A new study finds marathoners' knees free of osteoarthritis

Every runner has heard from a non-runner, “Isn’t running bad for your knees?” The answer from devoted runners has always been that it’s no worse than other sports (like skiing or hockey), but a 2019 study confirms that running isn’t so bad after all–even after 1,000 marathons.

A group of six runners who had completed over 1,000 marathons were recruited for the study. While the sample size was notably small, the results were encouraging. Researchers found that three of the runners had cartilage tears, and one runner had degeneration at the meniscus (which is common with age). None of the six runners showed osteoarthritis in the knee.

This study is in line with a recent paper out of the British Medical Journal that also found running wasn’t harming knees. The study looked at more runners, 82 this time, who received MRIs six months before and two weeks after running marathons. They found improvements in damaged subchondral bone (the layer of bone just below the cartilage) and also in the femur. Together, the femur and subchondral bone make up the main weight-bearing areas in the knee (so the areas that stand to affect a runner.)

Runner training knee pain

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The one area that running wasn’t shown to improve in the knee in the second study was the patellofemoral compartment–where the activity was actually shown to worsen the condition of the cartilage. However, researchers found that runners typically didn’t notice this change and reported no symptoms.

The key difference between the two studies is the experience level of the runners. The first study looked a highly experienced marathoners, whereas the second describes their participants as novice. In both studies, running was not reported to worsen knee conditions.

This isn’t to say that runners are immune to knee injury–knee pain remains one of the most common overuse injuries. What this means is that running isn’t inherently bad for your joints (and you can show this to all the people who’ve told you that it is).

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