The Washington Post: Does running really wreck your knees? “Contrary to popular opinion, distance running rarely causes knee problems in runners, and often leaves joints sturdier and less damaged.” By Gretchen Reynolds.

“Hart and his colleagues believe running strengthens the major leg muscles supporting the knee, allowing them to take on and offload more of the strains involved in repeatedly striking the ground.

The knee’s cartilage probably also bulks up, thanks to the repeated squishing it receives during running, Esculier said. “For a long time, we thought that cartilage could not adapt” to running or other activities, he said, because it lacks blood supply and nerves. “But in fact, cartilage does adapt,” he said, “by becoming stronger and more tolerant to compression.”

In a 2022 review of past MRI studies he co-wrote, he and his colleagues found evidence that the knee’s cartilage flattens immediately after a run, but then bounces back into shape within a few hours. With long-term recreational running, he said, the cartilage probably thickens, although that possibility still needs to be studied.

“Bottom line is that cartilage does become more robust” with running, Esculier said.”