awful
I've got arthritis in it pretty bad, and it gets 'stuck' a lot. The reconstruction required putting screws in the bones to hold the replacement, and one of them is working it's way out.
I did when I was about 15. It went pretty good, but I had to wear a leg brace and use crutches for about a month afterwards. I also had a torn ligament that they did nothing about. That got to have reconstructive surgery when I was about 28. That one was not fun, the scope was in and out, the...