My mom had them both done at the same time also, and they started rehab the day of the surgery. At that hospital, they did all the TKAs the same morning each week (or maybe every other week, not sure) and then did group rehab twice a day - it was extra tough for her because all the other patients were unilateral and she had to get through the exercises on both sides in the time they did just one - IIRC she was walking the length of the hall before her discharge. She started with OP PT three days a week right away.