"Running destroys your knees" is one of the most durable myths in fitness culture. It's also wrong, in ways the data has been clear about for thirty years.
The largest population study on the question, published in 2017, followed 75,000 runners and 14,000 non-runners over 21 years. The runners had 50% lower rates of knee osteoarthritis than the non-runners. Not equivalent rates. Half.
This finding has been replicated repeatedly. Recreational running, in the absence of prior injury, is now considered protective for knee health, not harmful.
What actually destroys your knees
Three things, in roughly this order:
Sitting all day. The combination of constant flexion and zero load creates a degenerative environment that the knee was not designed for. The deskbound office worker is at higher osteoarthritis risk than the marathon runner.
Carrying excess body weight. Each pound over your healthy weight transmits roughly four pounds of force through the knee with every step. Twenty pounds of belly fat is eighty pounds of additional load on a joint that is already loaded.
Previous injuries that were never properly rehabilitated. The torn meniscus from college that you walked off without seeing a doctor is the meniscus that becomes osteoarthritis at 55.
None of these are running. All of them are common.
The honest caveat
Recreational running, twenty to forty miles a week, on appropriate surfaces, in proper shoes, with adequate strength training to support the joint, is good for your knees.
Competitive ultra-running, ninety miles a week on hard surfaces, ignoring pain signals, with no supporting strength work, is not good for your knees.
Almost no one reading this is doing the second thing. The fear of running has scared millions of men out of the single most accessible cardiovascular activity in the world. The data does not support the fear.
