The end result is what it's all about! An arthritic knee will only get worse. A tkr pain will get better! Sounds good to me!
I had 13 rescued cats at the time of my surgery. I bought a long handled litter scooper, which was a real help. Of course, I had bought loads of cat food and litter ahead of time. I used a cup to scoop fresh litter into the boxes as needed. Hopefully, you can find someone to check on them while you're gone and come in every few days to check on you, too, once you're home.
Don't feel you shouldn't ask for help. You will be able to repay their kindness later, by doing something for them.I have a couple of neighbors that might pop by after work or something - the hardest part is (for me) is asking!!