Each person's situation is unique. But the comparison to having a crown done is ludicrous. I am 75 years old. I've had bi-lateral (both) TKR and bi-lateral hip replacements. My knees were done 6 weeks apart when I was 55 years old. Hips in 2010 and 2014. I was in #10 pain prior to the TKR surgeries, which is why the surgeon did not hesitate even though I was younger (65 or older was the norm 20 years ago). My therapist and I worked furiously to prepare me for the 2nd replacement six weeks later. I was grateful that I was young and fairly fit in spite of the limitations caused by severe knee arthritis. It took several months to get my full mobility back, but eventually the pain subsided. Not that I haven't had issues with muscles, ligaments and tendons, over the years. but at 20 years out I'm still doing well. These knees and hips have logged thousands of miles, many of them over rough terrain while hiking. Water aerobics in 4ft of 84+ degree water was without a doubt the most helpful therapy for both my knees and my hips.
Good luck creating a plan that works for you.