You have probably heard that running is tough on your knees and may cause long-term damage. But is this actually true? Running is a relatively high-impact activity. Each time your foot strikes the ground while running, your body absorbs a force equivalent to about two to three times your bodyweight. It is easy to imagine this load going straight into your knees, and to some extent it does: your knees absorb three times more load during running than walking. However, this is not necessarily a bad thing. In fact, running may help keep your knees strong and healthy.
Designed to Keep Moving
Your body is not simply a pile of bones and cartilage that gets worn down with every step. It is a living, dynamic system that grows and adapts in response to the loads placed upon it. And it needs load to keep functioning properly. Your knee joint is incredibly strong and designed to move. The cartilage inside your knee is a strong, flexible connective tissue that cushions and protects the bones of your knee joint. There is good evidence that when load is removed—for example, during prolonged bed rest or immobilisation—bone and cartilage begin to deteriorate.
Running’s Impact on Bones and Cartilage
We know that running temporarily reduces the thickness of knee cartilage, but this returns to normal a couple of hours after the run is finished. Researchers have suggested this may be an important process that facilitates nutrient movement into the cartilage, helping it adapt and become stronger. In support of this idea, evidence shows that runners tend to have thicker cartilage than non-runners, especially in their knees. Runners also tend to have better bone mineral density than non-runners. It has even been suggested that the more you run, the better protected you are against developing osteoarthritis, although more research is needed to confirm this. All of this points to running being beneficial for your knees’ health and longevity, even before considering the well-known benefits for heart and metabolic health.
But Am I Too Old to Start Running?
Unfortunately, to my knowledge, there is no strong evidence examining what happens when you pick up running later in life. However, other lines of research suggest it is likely safe and effective. A 2020 study demonstrated that older adults aged 65 and older who start high-intensity jump training, known as plyometric training, not only see improvements in strength and function but also find it safe and enjoyable. Considering that this type of training leads to much higher joint loads than running, it gives us a good indication that starting running in later life will also be safe and effective. However, you should still start slow. Like any type of exercise, your muscles and joints need time to adapt to the new load being placed upon them. It is best to start with intervals where you walk for a short period, then jog for a short period, gradually increasing your running distance over time, giving your body time to adapt.
Why Does Running’s Bad Reputation Persist?
I believe this myth persists because, despite all its health benefits, almost half of runners will get some kind of injury each year, and knee injuries are among the most common. However, the vast majority of these are overuse injuries caused by issues with load management rather than running itself. This means they are caused by people running too much too quickly without letting their bodies adapt and get stronger. All exercise comes with the risk of injury, so we will never completely eliminate the chance of getting hurt. But with respect to running, a few things can help.
- Progress slowly: Large spikes in how much and how often you run can lead to injuries. Try not to increase your mileage by more than a couple of kilometres per week.
- Eat enough to support your running: Running burns a lot of energy, and you need adequate energy available to recover properly after you run. Eating enough carbohydrates and protein to meet your energy and recovery needs might help prevent overuse injuries such as stress fractures. Some research suggests getting enough calcium and Vitamin D might do the same.
- Choose softer surfaces: There is some evidence that running on grass results in less impact than running on harder surfaces such as concrete. Doing a couple of your weekly runs on grass when you are first starting might be a good way to help you adjust to the load.
For most of us, the health benefits of running will far outweigh the risks—especially if you take it slow, build up strength, and keep listening to your body.
