Running and your knees: what twenty years of research really says

You are 48, you run three times a week, and at every birthday party someone asks whether you are wrecking your knees. The short answer from twenty years of research: probably not. The long answer is more interesting, and more honest.

A quick reading guide first. Every claim in this piece comes with a rating. Strong evidence means many randomised trials pointing the same way. Moderate evidence means large observational studies or trials with clear limitations. Still uncertain means lab measurements, small groups or research that is still running.

The big question: does running wear out your knees?

The most cited study is a 2017 meta-analysis in the Journal of Orthopaedic & Sports Physical Therapy. Eduard Alentorn-Geli and colleagues pooled 25 studies covering more than 125,000 people, of which 17 studies with almost 115,000 participants went into the statistical analysis (source).

Recreational running was linked to less osteoarthritis, not more. People who had run for less than 15 years also did better than controls. The higher figure among elite runners does suggest that years of very high volume and intensity may play a role.

Be clear about what this kind of research cannot do. It shows an association, not a cause. People with painful knees often stop running and no longer count as runners. And earlier knee injuries, such as a torn cruciate ligament, can skew the numbers. The authors say so themselves.

Evidence: Moderate. Large and consistent, but observational. It makes it likely that recreational running is not a special risk for your knees. It does not prove that running protects them.

How much force actually goes through your knee?

The image of "pounding your joints" is hard to shake. The best direct measurements come from people with knee replacements that have sensors built in. In a 2010 German study, five people with such an instrumented implant went through everyday movements (Kutzner et al.).

So walking down a flight of stairs asks more of your knee than a stroll. Running sits well above that: a 2014 study using motion capture and a computer model estimated a peak of about 8 times body weight, three times the figure for walking (Miller et al.).

That need not be a problem. When you run you take far fewer steps per kilometre and your foot spends less time on the ground. Per metre travelled, the load in that study was no higher than in walking: 0.80 versus 0.75 times body weight. That is one explanation for why runners do not get more osteoarthritis. A second, still unproven idea is that cartilage adapts to loads you give it regularly.

Evidence: Still uncertain. The measurements themselves are precise, but how they translate to your knee is not.

What if you already have osteoarthritis?

This is where the evidence is strongest, and the news is good. In late 2024 the Cochrane review on exercise for knee osteoarthritis was updated: 139 randomised trials with 12,468 participants (source). Exercise improved pain by roughly 9 to 13 points on a 100-point scale, and daily function improved too.

The authors are candid about the limits. The improvements were modest and did not clearly reach the threshold at which people notice a real difference. Participants also knew they were exercising, which may colour the results. They found no clear difference between types of exercise.

In October 2025 The BMJ published a network meta-analysis of 217 randomised trials with 15,684 participants that compared exercise types head to head (source). Aerobic exercise, such as walking, cycling and swimming, came out as probably the most effective for pain, function, gait and quality of life. Strength and mixed training also clearly improved function.

That one analysis names a winner and the other does not mostly tells you the differences between exercise types are small. The core message holds: moving helps. Whether running suits you if you have osteoarthritis is an individual call.

Evidence: Strong that exercise helps knee osteoarthritis, based on hundreds of trials, even if the effect is modest. Moderate that aerobic exercise is the best type: the BMJ authors rate their certainty as moderate.

Weight: every kilo counts four times

In 2005 Stephen Messier and colleagues studied 142 people with overweight and knee osteoarthritis who took part in an 18-month diet and exercise programme (source). Each kilo they lost was associated with roughly 4 kilos less force on the knee, per step while walking. Over thousands of steps a day, that adds up.

Evidence: Moderate. A clear and widely cited result, but measured in older adults with overweight and osteoarthritis, while walking. For runners at a healthy weight it is less well studied.

The real risk: that one run too long

Anyone who has been injured often knows it in hindsight: running was not the problem, doing too much too soon was. The Garmin-RUNSAFE study, involving researchers from Aarhus University among others, followed 5,205 runners from dozens of countries for 18 months through their sports watches (source). Their average age: 45.8.

The standout finding: single sessions predicted injury better than weekly volume. When one run was more than 10% longer than your longest run in the previous 30 days, injury risk rose. A run 10 to 30% longer raised it by 64%; more than doubling it raised it by 128%. Week-to-week comparisons showed no link.

In practice: if your longest run this month was 12 kilometres, 13 is a sensible next step. Suddenly running 18 is exactly the kind of jump that stood out in the data.

Evidence: Moderate. Large, prospective and based on real training data. But injuries were self-reported, they covered all overuse injuries rather than knees alone, and it remains an association, not a hard limit.

A Dutch study to watch

What is still missing is solid research on people who already have early osteoarthritis and stay active. Erasmus MC in Rotterdam is working on exactly that with the LoaD study (protocol). The plan: follow 300 active people aged 45 to 65 with knee osteoarthritis for two years, split across runners, cyclists, tennis players and hikers. Using MRI scans, blood tests and GPS data from their watches, the researchers want to see which activity, at which intensity, is linked to how the osteoarthritis develops.

According to the published protocol, recruitment was planned from September 2023 to October 2025, partly through Golazo, the organiser of the Rotterdam Marathon. There are no results yet. With two years of follow-up per participant, conclusions will take a while.

Evidence: Still uncertain. This study is under way.

What you can do today

1. Train your hips and thighs. For runner's knee, pain around or behind the kneecap, exercise therapy for the knee and hip plus education about load is the first choice. That is the conclusion of a large 2024 guide in the British Journal of Sports Medicine, based on 65 high-quality trials (source). Think squats, split squats, step-downs and side-lying hip work. Strong evidence that this helps existing knee complaints. Still uncertain whether it prevents injuries in runners without complaints: a 2024 meta-analysis found no clear overall effect, though supervised programmes did better (source).
2. Build from your longest run. Use your longest run of the past month as your reference and go beyond it in small steps. New plan, coming back from a break or trying trails for the first time? Start lower than you think.
3. Mix it up. Cycling, swimming and walking all count towards your fitness and give your knees a different stimulus.
4. Take pain seriously, without panic. A niggle that fades within a day is often part of training. Pain that stays or gets worse, swelling, a knee that locks or feels like it gives way: have it checked by a physiotherapist or your GP. In the Netherlands you can usually see a physio without a referral.

The honest conclusion

Twenty years of research, from Messier's weight study in 2005 to the BMJ analysis in 2025, points the same way. Recreational running does not appear to be a special risk for healthy knees; in the data, sedentary people tend to fare worse. For knees with osteoarthritis, exercise is one of the best-supported treatments available. What we do not yet know: whether running actively protects your knees, and exactly how running affects existing osteoarthritis. Studies like LoaD may shed more light on that.

This article is information, not medical advice. If you have knee complaints that do not ease after a few weeks, or you are unsure whether running is wise for you, see a physiotherapist or your GP.