This is a very pessimistic write up in my humble opinion. I am 81 years old. I had bilateral (sequential) total knee replacements in 2015. The right (done first) was much more painful than the left. I screamed when I walked 50 feet. I had some pain afterward cause of an irritated psoas muscle or nerve. That went away rapidly - maybe within the week at most (do not remember).
My knees feel totally normal - like my own. I have no pain or other issues. I do not ever kneel on them; do not have the need. Although I can easily run (my previous addiction), I do that only when I have to for some reason.
I also had a total hip and reverse shoulder. All feel like my normal parts. I totally forget about them. I never had a single physical therapy session except I met with a PT before they would release me.