Will running wreck your knees? Here's what the data say

"Running will wreck your knees." Buy your first pair of running shoes after 40 and someone is bound to tell you. It sounds like common sense, since every stride lands with a jolt and the knee absorbs it. Line up the research that has tested the claim, though, and it doesn't hold up well.

Women's Health ran a piece on aging knees in October 2026. In it, Abigail Campbell, MD, a sports orthopedic surgeon at NYU Langone, called it a misconception that getting older means you can't run without ending up with knee pain or arthritis. In 2025, mindbodygreen covered a survey of nearly 4,000 marathon runners presented at the annual meeting of the American Academy of Orthopaedic Surgeons. Neither weekly mileage nor pace was linked to more arthritis.

What osteoarthritis is, and why runners worry about it

Osteoarthritis is the wearing down of cartilage, the smooth tissue that caps the ends of your bones so the joint can glide. As it thins, the knee aches, swells and stiffens. Every running stride sends a small jolt through the knee, so it seems logical that running would speed up that wear. The question is whether the data back that up.

What 25 studies and 125,810 people showed

In 2017, Alentorn-Geli and colleagues published a meta-analysis in the Journal of Orthopaedic & Sports Physical Therapy. They gathered 25 studies covering 125,810 people and pooled the results of 17 of them, comparing hip and knee osteoarthritis in competitive runners, recreational runners and sedentary people who didn't run.

Osteoarthritis showed up in 13.3% of competitive runners, 10.2% of nonrunners and just 3.5% of recreational runners. Competitive meant professional or elite athletes, or people racing at the international level. Everyone else counted as recreational, which covers anyone who heads out for a few easy runs a week.

This next part is worth reading closely. The clear gap was between recreational and competitive runners. Compared with nonrunners, neither the lower risk in recreational runners nor the higher risk in competitive ones reached statistical significance on its own. And running for less than 15 years was associated with less osteoarthritis than not running at all.

Cartilage compresses a little, then seems to recover

What happens inside the knee right after a run? Coburn and colleagues at La Trobe University's sport and exercise medicine research center in Australia tackled that in a 2023 meta-analysis in Osteoarthritis and Cartilage. They pooled 24 studies that used MRI to scan 446 knees before a run and for up to 48 hours afterward.

Immediately after running, knee cartilage was 3.3% to 4.9% thinner or smaller in volume. In the joint between the thighbone and shinbone, one measure of cartilage composition returned to baseline within 91 minutes. Cartilage defects that were already there didn't change over the next 48 hours.

The authors concluded that a single run doesn't appear to harm knee cartilage, since the changes are small and seem to be short-lived. They also noted that the certainty of the evidence is very low and that there are no data on the hip.

More miles weren't linked to more arthritis

That leaves the volume question. Burfield and colleagues at Australian Catholic University and the University of the Sunshine Coast looked at it in a 2023 meta-analysis in Physical Therapy in Sport, covering nine studies and 12,273 people, 1,272 of whom ran regularly. The control group ran less than 8 km a week, roughly 5 miles.

Runners logging 8 to 32 km a week (about 5 to 20 miles), 32 to 48 km (20 to 30 miles) or more than 48 km (30 miles) had no more knee osteoarthritis than the controls. Overall, runners didn't differ from the control group. The authors urge caution, because five of the nine studies carried a high or very high risk of bias, and they call for large studies that follow people over many years.

What these studies can't tell you yet

First, they're observational. They compare people who already ran with people who didn't, so they can't prove that running protects the knee. People with healthy knees may simply keep running while those who get hurt stop. Alentorn-Geli's team acknowledged they couldn't separate out the effect of other factors, such as a previous injury.

Second, the competitive finding. In the first meta-analysis, years of high-volume or high-intensity running were linked to more osteoarthritis, although the difference compared with nonrunners wasn't statistically significant. A knee that already has osteoarthritis or an old injury is a different story, and that's your doctor's or physical therapist's call.

Third, according to mindbodygreen, the marathon survey's lead author, Matthew Hartwell, named age, body weight, family history and knee injuries or surgery as factors that do raise the risk of arthritis. If any of those apply to you, start more gradually and check in with your doctor first.

How to start running after 40 without fearing for your knees

If you don't run at all right now, don't try to run nonstop from day one. Mix short bouts of jogging with walking breaks and add a few minutes of jogging each week. Want a ready-made schedule? Our 8-week couch-to-5K running plan starts exactly that way.

The first meta-analysis is about recreational runners, and running three times a week puts you squarely in that group. Add strength work too. Squats, lunges and step-ups build the muscles around the knee, and you can fit them into the same week at Gym Triple X. If your knees already bother you, here's what actually helps an arthritic knee. Pain that doesn't settle within a few days is your cue to stop and get it checked.

Taking up running after 40 is less about courage than about pacing. The trick is knowing when to add minutes and when to hold back. If you'd like someone to map that out week by week, a personal trainer on the Costa del Sol can tailor it to your knees and your schedule.