Does running ruin your knees? What 125,000 people tell us

"You'll wreck your knees" is one of the most common things runners hear. As a surgeon who replaces worn-out knees for a living, I understand why the idea sticks: a knee is a joint, running loads it, and loading must wear it out. The research tells a more interesting story.

What the biggest review found

A systematic review pooled 25 studies covering about 125,000 people, and combined 17 of them — about 115,000 people — in a meta-analysis comparing runners with non-runners. Runners were called competitive if they were professional or elite athletes or took part in international competition, and recreational otherwise.^[1]

The share of people with hip or knee arthritis was:^[1]

Recreational runners had the lowest rate of the three groups.

The detail most headlines skip

When the authors calculated the odds of arthritis against non-runners, neither group was clearly different from non-runners on its own: the result for recreational runners leaned lower and for competitive runners leaned higher, but both ranges crossed "no difference". The clear, statistically strong difference was between recreational and competitive runners.^[1] People who had run for less than 15 years also had lower odds of arthritis than non-runners.^[1]

The authors' summary was that both a more sedentary lifestyle and long exposure to high-volume or high-intensity running were associated with hip and knee arthritis.^[1]

Why this is an association, not a promise

These studies observed people; they did not assign anyone to run. Runners may differ from non-runners in weight, injuries, genetics and much else, and people with sore knees may stop running. The authors themselves said they could not tell whether the links were causal or explained by other factors such as previous injury.^[1]

That is why "recreational running protects your knees" is graded only C here, while "recreational running wears out your knees" is graded D: the largest review we have points the other way.

What this means in practice

• For most people, running at a recreational level does not appear to be the knee-wrecker it is often made out to be.
• Very high-volume, elite-level running over many years is a different exposure.
• A previous knee injury — a torn ligament or meniscus — changes the picture and is worth discussing with a doctor before you build up your mileage.
• If running already causes knee pain, swelling or locking, get it assessed rather than pushing through.