I had a hip replaced a month before I turned 47 (I'm 54 now). Before that, I had to do all kinds of weird rolling around like a turtle to get myself back up off of the floor to work around my bad hip. Kind of like when Starsky and Hutch would run and roll as they were getting shot at - but much slower! It was almost impossible for me to get up without using my hands and arms. It's better now, but I still have to be careful and protect that expensive, bionic hip. I'll probably have to have the other one replaced eventually. When I was still recovering from my surgery, I put a different rearend in my '64. I was laying on my side trying to protect my new, healing hip while I was lining up one of the leaf springs with the front hanger and then, POP! I partially tore my biceps. LOL If it's not one thing, it's another!
With my bad hip, I was able to use my knees a lot, so I can imagine how hard it would be to not be able to use your knees as much, Steve. I don't have any good ideas for how you can get to the floor and back without relying a lot on your knees. As has been suggested, padding should help, though.
I read this thread to my wife. Interesting how many in our group are getting to the age where these physical issues of ours are as prevalent as the mechanical issues of the cars we have!