Trail Notes | Strength, Injury & Recovery

what the kms are really doing

Does Running Wear Out

Your Joints?

Running places repeated load through the hips and knees. That does not mean it slowly wears them away.

Many runners have been warned that their kilometres will eventually catch up with them. The idea sounds logical. If running loads a joint thousands of times, surely the cartilage must eventually run out.

But joints are not machine parts. Living tissue responds to appropriate load. Bone, muscle, tendon and cartilage all exist within a body capable of adaptation.

The research does not show that recreational running inevitably causes knee or hip osteoarthritis. It suggests a far more reassuring and more nuanced picture.

Trail Note  ·  01

What the often-quoted numbers mean

A 2017 systematic review and meta-analysis pooled findings from 25 studies involving more than 125,000 participants. It reported different rates of hip or knee osteoarthritis across three broad groups.

These figures are reassuring for recreational runners, but they need to be interpreted carefully. They describe associations across different studies. They do not prove that recreational running prevented arthritis or that competitive running caused it.

The groups differed in more than running volume. Age, previous injuries, joint surgery, body composition, occupation and sporting history can all affect osteoarthritis risk. Competitive runners may also carry years of injuries and high-level sport exposure that cannot be separated neatly from mileage.

Trail Note  ·  02

Osteoarthritis and running pain are not the same thing

A runner can experience knee pain without having osteoarthritis. A person can also have changes visible on an X-ray without experiencing significant pain.

Common running problems such as patellofemoral pain, tendon irritation or a reaction to a sudden increase in load are different from a diagnosis of osteoarthritis. They require their own assessment and management.

This distinction matters because “my knee hurts after running” can quickly become “running is ruining my knees.” The first statement describes a symptom. The second assumes a cause and a diagnosis that may not be present.

Trail Note  ·  03

What appears to matter more than mileage alone

A study of active marathon runners found that running history, weekly mileage and the number of marathons completed were not independent predictors of self-reported hip or knee arthritis within that sample.

Age, family history and previous joint surgery were associated with arthritis. That does not make mileage irrelevant in every circumstance, but it challenges the idea that kilometres alone determine whether a runner develops joint disease.

Trail Note  ·  04

There is no universal safe mileage

Research has not identified one weekly distance at which healthy running suddenly becomes damaging. The same distance can be manageable for one runner and excessive for another.

Capacity depends on training history, current health, terrain, intensity, recovery and what else the person is carrying. Fifty kilometres built over years is a different physical request from fifty kilometres reached through a sudden training jump.

This is why a good program cannot promise safety through a single percentage or kilometre ceiling. It manages the relationship between load and the runner’s current ability to absorb it.

Trail Note  ·  05

How to support your joints for the long run

Not every ache requires complete rest, and pain does not automatically mean damage. But it does give you information about what your body is currently tolerating.

A physiotherapist or appropriate health professional can help identify what is contributing and build a plan that keeps movement in your life where possible.

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