Hey Trish4,
One more thing to think about: you don't need general anesthesia! I've had two complete knee replacements myself. I had what is called a minimally invasive procedure with Dr. Richard Berger at Rush in Chicago. I did NOT have general anesthesia, just twilight + epidural. You can have the surgery and leave the same day. Loads of people travel from around the world to go to him. He and his colleagues have been doing the minimally invasive without anesthesia for at least 10 years. I don't know where you live, but you should look into it, you don't have to have general!
Knee replacement is not fun, I won't lie, but you definitely MUST do it. Don't do both at once, space them at least a few months apart. Go religiously to physical therapy BEFORE and after and you'll be fine (and so happy that you can walk, run, and jump without pain!) The only thing I definitely cannot do is some yoga positions where you have to sit back on your heels, just does not work!
Good luck.