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Yeah, longboarding was acutally the funniest, because I suddenly started to look for steep streets with narrow corners and I find them really beautiful.
I mean something so simple as a piece of asphalt suddenly becomes attractive in a way :D

I can imagine I never got into it myself and I am not sure why but it does look like such fun
Not that I would try it now my knees aren’t what they used to be

Yeah, it's probably not a good idea, because especially slides can be rather hard on the knees.

The last time i tried skiing my knee popped out of joint and i understand long boarding is harder on the knees so for sure not for me

Uh, that sounds bad. I hope you recovered completely after that accident!
I think it depends on what your want to do with a longboard.
If you just use it for cruising around and you start to learn it step by step, it's rather soft on the knees.
But all further from that has a higher risk for injury.

It was maybe 20 Years ago and I recovered fine from it has happened a few times over the years I smashed both knees when I was 19 but that didn’t slow me down for long but I feel it now as approach my 60s lol

Thats very good, that you recovered that fast!
I had broken my foot while climbing 6 or 7 years ago and I still have to deal with it today sometimes.
Injuries at the joints can be nasty.