I agree it feels like there's a reflex to avoid it! My knees started swelling when I was in my 20's if I tried to kneel on them, so I got used to sitting on the ground for all my gardening and other chores. After my TKR I just "felt" like I wouldn't be able to get up off the floor if I sat down, because of that brief time I'd need to transition from sitting on the floor to standing. I'd read that something like half of us simply feel uncomfortable kneeling after the TKR. One day, about a year after the TKR, I just suddenly felt I could do it! I sat on the floor to fix something, then stood back up the way I used to do it! Wow! That brief contact with the floor wasn't bad at all. Now I am much more confident about doing the things I used to do.