I was diagnosed with "you-gonna-die" cancer in 2017. Chemo and radiation for six months. Declared clear in January of 2018.
But man-o-man, my knees hurt. They'd hurt for years. But with an unexpected new lease on life, I thought, "How hard can it be, given what I just went through? Let's fix 'em!"
Knee surgeon said lose weight or he would not operate. Fasted one day, actually 36 hours, a week, for eight months or so. Lost about 50 lbs.
Replaced the knee.
Yeah, it was painful. Not the op, but the rehab part is hard. But the results are great! And after surviving the "you-gonna-die" cancer diagnosis, psychologically I was "bring it on! Show me what ya got!" The physical pain is small beer compared to the stress of a dire cancer diagnosis.
I was ready. Worked my butt off with the rehab and recovery was great. Then had the other knee done a coupla years later.
Like everyone says, take the rehab very serioiusly. Knock yourself out on it. It makes all the difference in the world.
Best wishes.