Myth Busting Monday: Is Running Bad for Your Knees?

When I share that I am a runner, I am sometimes met with worried looks and “aren’t you worried about your knees?” Similarly, I have heard clients say things along the lines of “I know at my age I probably need to stop running to protect my knees,” or “I used to run a lot in my 20s but I wore my knees out,” or “I’d like to get back to running but I don’t want to destroy my knees.” Many people hold the belief that our knees have a set lifespan, and that running shortens the warranty on knee function.

Well, I’m here to tell you to lace up your shoes and go run without fear, because the research supports that running is NOT bad for your knees. Let me say it again – running is not going to magically “wear out” your knees and cause you to have worse arthritis. Remember that exercise is generally good for your body and fear-mongering messaging that some forms of exercise may hurt you is likely to cause more harm (preventing people from participating in a widely accessible form of exercise that can decrease metabolic risk factors associated with all cause mortality, improve mood, generate community…) than good.

The facts:

• This 2023 systematic review and meta analysis looked at knee cartilage thickness immediately (<20 min) and delayed (>20 min to 48 hours) after running. They found a transient decrease in cartilage thickness immediately after running that recovered to baseline thickness at an average of 91 minutes post-run. Those who had cartilage defects at baseline demonstrated no change in those defects after running. That initial decrease in cartilage thickness may sound scary, but I want you to think about your cartilage like a sponge. Activities that load the knee, involve impact, or even just prolonged standing (thanks, gravity) apply downward force to the sponge, causing fluid to be pressed out and the cartilage to be slightly compressed. Luckily, like a sponge, with time the fluid resorbs and the cartilage returns to its original height!

  
  

• In 2013, Williams examined the frequency of hip osteoarthritis and replacement risk between walkers and runners. They found that running had a PROTECTIVE effect (ie less risk) on hip OA and replacement. The authors speculate that this is due to the lower BMI of the running group. Running can be a great way to exercise and maintain a healthy weight, which reduces general OA risk.

  
  

• Additionally, this meta-analysis of 17 studies by Alentorn-Geli et al. concluded that recreational runners have significantly lower rates of hip and knee OA than sedentary non-runners (3.5% prevalence vs 10.2%), while competitive (running in the elite or professional fields) only demonstrated a modest increase in hip and knee OA prevalence (13.3%).

  
  

• Similarly, in 2023, Burfield et al. performed another systematic review and meta-analysis aimed to find a connection between running weekly volume and OA prevalence. They found no change in OA prevalence between any running volume and controls.

If running is a relatively higher impact form of exercise, how could it not negative affect joint health? Well, in addition to load cartilage and joint surface, it also loads the muscles around the joints, strengthening them and making them more resilient to these forces and able to withstand these loads. Muscle strength can also help reduce OA symptoms by offloading the joint. Regular movement, including running, can help improve joint mobility, which is important for maintaining function and reducing pain. Finally, joint compression acts to “feed” the cartilage. Remember when I said cartilage is like a sponge? It is and doesn’t have a robust blood vessel system to bring nutrients and take away waste. Instead, cyclical compression and relaxation of forces help to circulate synovial fluid and bring nutrients to the cartilage and carry away waste.

In summary, many people develop osteoarthritis. Some people have more symptomatic and limiting arthritis that may lead to the need for medical intervention or even surgery. But whether you spend your days on the couch, walking, or running, there does not seem to be a significant difference in risk of developing osteoarthritis or needing a joint replacement. So, if you like running, run! Don’t sit out because you’re worried about the long-term effect on your hips or knees. Keep up your strength and mobility exercises to help you have longevity in the sport and stay active and mobile into the later decades of your life. And if you don’t like running, pick another form of exercise that makes you happy! Motion is lotion for your joints, so keep moving in whatever way you enjoy.

Thanks for reading!

Dr. Elizabeth Karr PT, DPT, OCS