I Have Been Told That I Will Need Both Knees

I have been told that I will need both knees replaced, because there is no cartilage in one knee and the other is almost gone also. Is it possible too have both knees done at same time? I am in my mid 60 and a about 50 pounds over weight, but stay busy most of the time and have a very high pain threshold. Is there a preset amount of down time (in hospital) I have Medicare part A & B and F plan with State Farm any idea how much out of pocket (roughly)