Completely immobilized? My Lacey had her left knee done twice (long story) and is having her right knee done this Thursday. We were never told to keep her completely immobilized. She was allowed to walk around in the house. No running, playing with our other dog, or going up and down the stairs too much. She is a very hyper dog and somehow we managed to survive. We have her leashed outside at all times because she might see something and take off running.
Good luck with you pups surgery and recouperation.