IS RUNNING BAD FOR YOUR KNEES?

All runners have heard the saying “But isn’t running bad for your knees?” At some point.  I know I definitely have!

It’s a hard myth to shake—especially when there’s a lot of anti-running rhetoric out there. Or someone telling you “they messed up their knee from running years ago.” The good news? Research has been pretty consistent in saying otherwise.

Yes, running does load your joints. It’s essentially a series of single-leg hops, so no one’s arguing that your knees aren’t working. But “stress” doesn’t automatically mean “damage.” In fact, multiple studies have found that recreational running is not associated with an increased risk of knee osteoarthritis.

A large 2021 systematic review and meta-analysis found that running may be beneficial for knee health. The theory is that the repetitive loading and unloading of the knee during running helps nutrients move into the cartilage while metabolic waste products—like excess water—get squeezed out. Since cartilage helps absorb shock and allows your bones to move smoothly, this process may actually help keep it healthier over time.

The same review did find a short-term increase in a biomarker called cartilage oligomeric matrix protein (COMP), which is associated with osteoarthritis. But that spike was temporary—levels returned to normal within an hour. (Another reason why recovery is so important!) Importantly, researchers found no negative changes in cartilage thickness or volume, which are key markers we worry about with osteoarthritis.

This wasn’t a one-off finding. A 2017 study looking at over 2,600 adults found no increased risk of knee osteoarthritis in runners compared to non-runners. Even more interesting: research suggests that running isn’t just safe for people without knee osteoarthritis—it may also be safe (and helpful) for people with it. A 2019 study following more than 1,000 adults over age 50 with knee OA found that running didn’t worsen pain or joint structure over time and was actually associated with reduced knee pain.

Now, does that mean runners never have knee pain? Definitely not. The knee is the most commonly injured area in runners. Issues like patellofemoral pain syndrome (PFPS), IT band syndrome, and patellar tendinopathy pop up frequently—but these are usually related to things like training errors, strength imbalances, or biomechanics, not cartilage breakdown. The good news is that these injuries are typically treatable in an outpatient physical therapy setting and, in many cases, fully reversible.

So how do runners’ knees handle all that repetitive loading? One explanation is adaptation. In addition to improved cartilage nutrition, research suggests that cartilage itself may change over time to meet the demands of running. A 2020 study found that medial knee cartilage appears to adapt as runners age, helping it tolerate years (or decades) of mileage.

In other words, runners don’t have “bad knees.”

They have resilient ones.