I had both of my knees replaced at the same time in May 2010. I am so glad I did. I never even think of my knees anymore and do anything I want, except kneel. I still do not like the pressure on them.
I was walking with a cane at 3 weeks, driving myself at 4 weeks. Before surgery, I could not walk. Right leg was bent and bowed out. I used the scooter in Walmart.
The best advise I can give you is DO EVERYTHING they tell you to do and more. Every exercise!!! If you don't, you will not bounce back and regain flex and extension.
The only thing they didnt tell me was my skin on the outer side would feel numb after. The nerve gets cut so now it has a funny sensation. I only notice this if my skin is touched like shaving my legs or putting on lotion.
Some doctors do not like doing both legs at the same time. You have to be in good health otherwise and under 70. I was 68. He told me he would do the right one first in case he had to bail out.