Is running bad for your knees?
No, the opposite: recreational runners had arthritis of the hip or knee less often (3.5%) than people who did not run (10.2%).
These are observational studies, so part of the difference is that people with bad knees run less. What they do rule out is the idea that ordinary running wears joints out: if it did, the runners would be worse off, and across 125,000 people they were not.
The dose does seem to matter at the top end, where competitive runners came out worse than both groups. For everyone else the risks are the familiar ones, mostly from adding distance too fast. Strength training for the legs is the one measure with trial evidence behind it.
Sources
2
- Alentorn-Geli, E. et al. (2017). The association of recreational and competitive running with hip and knee osteoarthritis: a systematic review and meta-analysis. J Orthop Sports Phys Ther 47(6). 25 studies, 125,810 people: arthritis in 3.5% of recreational runners, 10.2% of non-runners and 13.3% of competitive runners.
- Lauersen, J.B. et al. (2014). The effectiveness of exercise interventions to prevent sports injuries: a systematic review and meta-analysis of randomised controlled trials. Br J Sports Med 48(11). Strength training cut sports injuries to less than a third; stretching did not.