Yes, I noticed this too. I ran a lot in high school / university, and for some reason we mostly ran on the roads. In my late 20s a doctor told me my knees sounded like they were "65".

I read a book my Michael Colgan at the time, and he mentioned training athletes on the trails as much as possible to reduce injury, so I gave it a try ...

That was 25+ years ago. At first people looked at me strange, like I was running from an animal. But its common now, and I'm still running on the trail, and knees seem OK.

Yes of course, you can still trip, step on a snake, etc, but its a different kind of injury. You are adapting gait and balance constantly which is nice too.

Running on the trail is much more interesting, with constant change, ups, downs, variations. Whereas running on grass / asphalt I can go into autopilot mentally and start ruminating, this is harder on the trail and I am more in a state of "here and now".