Running has long been accused of wearing out your knees. But does repeatedly pounding the pavement really damage your joints? The research is more reassuring than you might expect.
If you run regularly, someone has probably warned you about your knees.
The argument sounds perfectly logical. Running puts considerably more force through the knee than walking. Repeat that impact thousands of times, several days a week, over several decades and surely something eventually has to wear out.
Except the human knee isn’t a car part.
Our joints are living biological structures capable of responding and adapting to load, and research has increasingly challenged the idea that recreational running inevitably leads to damaged knees or osteoarthritis.
That doesn’t mean every knee loves every run. But for most recreational runners, the evidence is far less alarming than the reputation running has acquired.
Does running wear out your knees?
The short answer is: there is little evidence that ordinary recreational running simply wears away healthy knees.
A 2023 systematic review examined 17 studies involving more than 14,000 runners and non-runners. It found no significant differences in several measures of radiographic knee osteoarthritis or cartilage thickness between the groups. In fact, knee pain was more common among the non-runners in the studies analysed.
The researchers concluded that, over the periods studied, running wasn’t associated with worsening radiological signs of knee osteoarthritis.
Another 2023 meta-analysis looked specifically at running volume. Across more than 12,000 participants, it found no significant difference in knee osteoarthritis prevalence between runners and controls. Even when runners were divided according to weekly distance, the analysis didn’t find evidence that the higher-mileage groups had greater osteoarthritis prevalence. However, many of the studies had a high risk of bias, so this shouldn’t be interpreted as proof that mileage can never matter.
The important point is that the familiar equation, more running equals more worn-out knees, isn’t supported by the evidence we currently have.
What actually happens to cartilage when you run?
This is where things become particularly interesting.
Researchers can use MRI scans to examine cartilage before and after running. A systematic review and meta-analysis found small reductions in knee cartilage thickness and volume immediately after a run.
That might initially sound like evidence of damage.
But the changes appeared to be temporary. Some MRI measurements returned to baseline relatively quickly, and existing cartilage defects didn’t appear to worsen following a single bout of running. The researchers concluded that these small, transient changes didn’t suggest that a run was detrimental to knee cartilage.
In other words, seeing a temporary change after exercise isn’t the same thing as seeing permanent damage.
Our bodies are exposed to mechanical stress whenever we exercise. That is also how bones, muscles, tendons and other tissues receive signals to adapt.
What about arthritis?
Osteoarthritis is often described as simple “wear and tear”, but that description is increasingly considered too simplistic.
Age matters, but so do previous joint injuries, genetics, body weight and other biological and mechanical factors. Running is only one possible source of load on the knee.
An influential meta-analysis involving more than 100,000 people found a lower prevalence of hip and knee osteoarthritis among recreational runners than among both competitive runners and sedentary controls.
That doesn’t prove recreational running prevents arthritis. People who run recreationally may differ from non-runners in numerous ways, and observational research cannot neatly separate all of those factors.
But it does make one thing difficult to argue: if recreational running routinely destroyed knees, we would expect the epidemiological evidence to look very different.
Running can still make your knees hurt
Here’s where an important distinction gets lost.
Running not being inherently bad for your knees does not mean running cannot cause knee pain.
Runners experience injuries like everyone else. Patellofemoral pain, often loosely called “runner’s knee”, is one example. Tendons, muscles and other structures around the knee can also become irritated.
Pain is particularly likely to appear when the amount of running someone is doing exceeds what their body is currently prepared to tolerate.
Imagine someone who hasn’t run for six months suddenly deciding to run five times a week. Their cardiovascular fitness may allow them to complete the sessions, but that doesn’t necessarily mean all of their tissues are ready for the sudden increase in load.
The problem in that situation isn’t necessarily running itself. It may be the transition from very little running to a lot of it.
Previous injuries matter
One of the biggest weaknesses in the simple “running ruins your knees” argument is that not all knees start in the same condition.
A person who has experienced a significant knee injury may have a different long-term risk profile from someone who hasn’t. Previous joint injury is a recognised risk factor for osteoarthritis, and it can complicate research attempting to separate the effects of running from everything that happened to a knee beforehand.
This is also why population-level findings shouldn’t be interpreted as personal medical advice.
The fact that recreational running appears broadly compatible with healthy knees doesn’t mean someone recovering from an ACL injury, meniscus injury or persistent knee problem should automatically follow the same training plan as someone with no history of knee trouble.
Is more running worse?
This is where the evidence becomes less certain.
Research comparing recreational and competitive runners has suggested that the relationship may not be as simple as “running versus not running”. Competitive athletes can accumulate enormous training volumes over many years and may also experience more injuries.
The 2017 meta-analysis that found relatively low osteoarthritis prevalence among recreational runners found higher prevalence among competitive runners. However, the researchers couldn’t establish that running itself caused the difference, because factors including previous injury could have contributed.
More recent analysis of weekly running volume has also failed to find a clear increase in knee osteoarthritis prevalence as mileage rises, but the quality of the available evidence means we should be cautious about declaring that there is no upper limit at which risk changes.
For the average person jogging several times a week, however, elite-level mileage isn’t particularly relevant.
What if you already have osteoarthritis?
Perhaps surprisingly, having knee osteoarthritis doesn’t automatically mean running is forbidden.
A study involving people over 50 with established knee osteoarthritis found that self-selected running wasn’t associated with worsening radiographic disease or increased knee pain over the follow-up period. Runners were actually more likely to report improvement in frequent knee pain, although observational findings like these cannot prove running caused the improvement.
That doesn’t mean everybody with arthritis should start running tomorrow.
The severity of the condition, symptoms, previous activity level and other health factors all matter. Someone with diagnosed osteoarthritis who wants to begin or significantly increase running should discuss what is appropriate with a healthcare professional or physiotherapist.
But the old assumption that arthritis automatically means avoiding impact exercise is too simplistic.
So should you worry about your knees?
For a healthy recreational runner, fear of “wearing out” the knees isn’t strongly supported by current research.
A better concern is how you run and how quickly your training changes.
Build running gradually rather than suddenly doubling your workload. Give your body time to adapt. Strength training can complement running by developing the muscles involved in controlling and supporting the lower body. Recovery matters too, particularly when increasing distance or intensity.
Most importantly, don’t treat persistent pain as something that has to be ignored to prove you’re a serious runner. Pain that continues, worsens, follows an injury, causes significant swelling or affects normal daily movement deserves proper assessment.
Is running bad for your knees?
For most recreational runners, the evidence is reassuring.
Running places substantial forces through the knees, but that doesn’t mean those forces inevitably damage them. Systematic reviews have generally failed to show that recreational runners develop more knee osteoarthritis than non-runners, and short-term changes seen in cartilage after running appear to be small and temporary.
There are important exceptions and uncertainties. Previous injuries matter. Persistent pain matters. Extremely high training volumes are less well understood. And no population study can tell you exactly what is happening inside your particular knee.
But if you’ve been avoiding running solely because someone told you that every kilometre is gradually wearing away your joints, the science offers considerably more reassurance.
Your knees aren’t tyres.
And running doesn’t come with a predetermined mileage at which they need replacing.
Further Reading
How to Pack Light for Any Trip
Stay Connected
Subscribe to the Together Magazine newsletter for thoughtful features, personal development insights, cultural recommendations, museum exhibitions, events in Brussels and Belgium, and the latest stories delivered directly to your inbox.
