In reply to David Coley:
My knees are going too ! I'm 48, but i first became aware of knee problems when i was in my early 20's, when i realised i had to give up cross country running, and street running, because it got too painful.
I don't know what started it, but cartilage damage can build up pretty quickly it seems.
I remember as a kid whilst laid belly down on bed reading, i often bent my lower legs up + down continuously for several minutes because i liked the clicking noises i could make my knees do...!
Then we had compulsory cross country runs at school wearing just gym plimsoles / pumps!
If you live anywhere hilly, the downhill running bits are highly abusive to your knee cartilage.
In my mid 30's i had already started trying to avoid jumping off stuff, especially at work. Kneeling down with legs fully folded would be ok for a few minutes but then sometimes surprise me with some nasty pain.
My left knee took some harsh unwanted abuse when during a demo an authority person threw me to the ground landing me on my knees and held me in one of those martial arts lock down positions for a few minutes.
Now, jumping off from only a few feet up, feels ok at the time, but not the next day. Rock overs get me worried too.
This year i'd like to have a plan to get outside more for bouldering, (and routing), but jumping / slipping / falling off boulder problems, even onto matts, probably won't be possible with my dodgy knees, unless i have an op soon.
This article here is inspiring...
https://www.ukclimbing.com/news/item/70456/fri_night_vid_alex_puccios_road_...
Post edited at 10:57