Is Running Bad for Your Knees?

_{Originally published at https://finishlinept.com/team-finish-line/runningmyth-knees/}

Whether you’ve been running for 10 years or 10 days, you’ve likely gotten this question when disclosing your healthy habit: “But isn’t running BAD for your knees?” It can be hard to argue with individuals who’ve been listening to anti-running propaganda for their entire lives, but fortunately there’s plenty of research to disprove this myth.

Although running certainly puts stress on your joints — it’s a single limb hopping activity, after all — multiple studies have found that recreational running is not associated with an increased risk of knee osteoarthritis. In fact, multiple studies, including a 2021 systematic review and meta-analysis (AKA, a study that synthesizes data from a wide variety of other studies) found that running can actually be advantageous for your knees. By loading the knee joint during running, researchers believe you’re actually helping to facilitate nutrition penetrating into the cartilage of your knees while simultaneously squeezing out metabolic substances, like water. Since cartilage assists the movement between your bones, as well as absorbs shock and transfers load through your bones to reduce friction, this is an act of service for your joints that can actually help protect them. 

While this particular review did find that running has a short-term adverse effect on cartilage oligomeric matrix protein (COMP), a biomarker (or indicator) of osteoarthritis, this increase was only temporary, with levels returning to normal within 1 hour. No adverse effects were found on knee cartilage volume or thickness, which are both often affected by OA.

Although the 2021 systematic review was pretty conclusive (researchers combined and synthesized results from two randomized controlled trials and 13 cohort studies), other research exists to back up its results. A 2017 cross-sectional study taking into account 2637 community adults found no increased risk of knee osteoarthritis among self-selected runners compared to non-runners. Other studies have found that not only is running not harmful for individuals with osteoarthritis, but it can even be beneficial: A 2019 cohort study from the Osteoarthritis Initiative that analyzed over 1,000 adults over 50 with knee osteoarthritis found that not only was running not associated with longitudinal worsening of knee pain or structure degradation, but running also helped reduce pain in individuals with knee osteoarthritis. 

Of course, some individuals will experience knee pain throughout the course of their running career, as the knee is the most commonly injured body part in runners. But these injuries — including patellofemoral pain syndrome (PFPS), iliotibial band friction syndrome (ITBFS), and patellar tendinopathy (PT) — are often due to overuse, muscular imbalances and weaknesses, and faulty biomechanics. Not only can these injuries typically be treated in an outpatient orthopedic physical therapy setting, but they’re also reversible. 

This evidence may seem confusing, and it’s normal to wonder how exactly a runner’s knees can withstand so much loading, so often. Some researchers think that in addition to providing nutrition to your joints and keeping cartilage healthy, your cartilage also goes through changes to keep up with your running habit. A study from 2020 suggests that medial knee cartilage likely adapts in runners as they age in order to withstand a lifetime of running — proving that runner’s knees aren’t “bad,” they’re just resilient.