Is running good or bad for your knees? A systematic review and meta-analysis of cartilage morphology and composition changes in the tibiofemoral and patellofemoral joints.

Runners and clinicians often wonder whether the repeated impact of running wears down knee cartilage over time, so this review pooled studies using MRI scans taken shortly before and after running to see what actually changes. Across 24 studies covering 446 knees, cartilage thickness, volume, and composition-related measurements consistently dropped right after a run, with some declines reaching double digits in certain regions. What makes this interesting is that one of these composition measures, T2 relaxation time in the tibiofemoral joint, returned to its starting level within about 90 minutes, and existing cartilage defects stayed unchanged within two days. That pattern suggests these post-run changes may be temporary rather than signs of damage building up.

However, the evidence behind these findings was rated very low certainty, only a third of the included studies were judged low risk of bias, and the review only looked at the knee, since hip cartilage data were not available.

If you run and have ever wondered whether it's slowly wearing down your knee cartilage, this review looked at exactly that question using MRI scans taken before and shortly after running. Pulling together 24 studies involving 446 knees, researchers found that cartilage thickness and volume measurements were lower right after a run, and some internal cartilage quality measurements dropped too, in some cases quite a bit. The encouraging part is that one key measurement of cartilage quality in the main knee joint bounced back to its starting point within about an hour and a half, and any cartilage damage that was already present didn't get worse within two days of running.

This hints that what happens to cartilage right after a run may settle back down rather than represent lasting harm. Still, the researchers rated the overall evidence as very low certainty, and only about a third of the studies had a lower risk of bias. The review also couldn't say anything about the hip, only the knee was studied.

This is a summary of research, not medical advice. Talk to your own healthcare provider about anything affecting your care.

This review addresses a question physiotherapists often field from runners: does a single run cause measurable harm to knee cartilage, as seen on MRI? Pooling 24 studies covering 446 knees, the synthesis found consistent immediate post-run reductions in cartilage thickness and volume (ranging from 3.3% for weight-bearing femoral cartilage volume to 4.9% for patellar cartilage volume) along with reductions in T1ρ and T2 relaxation times, the largest being 13.1% in femoral trochlear cartilage. What is clinically relevant is that tibiofemoral T2 relaxation times recovered to baseline within 91 minutes, and existing cartilage defects were unchanged within 48 hours post-run. This pattern is consistent with transient, load-related cartilage response rather than acute structural injury from a single bout of running, which may inform reassurance-oriented conversations about running and knee health, though this remains an interpretation drawn from low-certainty evidence rather than an established fact. The authors rate overall certainty as very low, with only about a third of included studies at low risk of bias, and the review covers only the knee, since hip cartilage changes remain unknown.

It also only captures single-session, short-term effects, so it does not establish anything about cumulative or long-term effects of repeated running on cartilage health or osteoarthritis risk.