[Eupraxias]

This is dangerous. My friend blew out his knee pushing too hard with trailrunning, and now he can never run again.

[alistairSH]

"Blowing out a knee" is a completely different issue to osteoarthritis of the knee.

[nradov]

If you fall due to tripping over a rock or something then of course you can damage your knee. The point is that running a lot won't necessarily wear your knees out.

[iamacyborg]

Telling people not to run due to a misconception about perceived harm is much more harmful than the risk of a serious knee injury from running.