I've had one knee done and healing was surprisingly ok. Bruised like hell, but walking around wasn't anywhere near as bad as I'd imagined. I've been doing martial arts for years and years so have similarly banged up/calloused knees, I need a bit of a skim over to on the lower part of my knee but generally I'm really pleased with how well it all held up. Best of luck with yours!
I'm currently a couple of days into healing a trad bear head on the side of my lower leg. I thought it was going to be a breeze as I've had stuff in the vicinity before but this one has blown up! Major fat leg issues going on and unusually for me I've already got big thick scabs, so that's not feeling great right now. I'm hoping the fast reaction will mean fast healing, but we'll see...