I am sorry to hear about your surgery. As it is, I sit here with both of my shoulders basically immobile. I have a suspicion I have torn the rotator cuffs on both shoulders. I woke up this morning unable to move my arms very much without severe pain-this follows my intense boot camp style workout a few days ago. Needless to say, I will be returning to my orthopedist tomorrow.
I injured my left shoulder about 2 months ago, and he gave me some recovering exercises that I performed. I just took it slow, and eventually I got almost back to where I was before. Well, until the unfortunate workout.
Could you swim? I think swimming would be great to build up some of what you lost without the weight bearing concerns. Or maybe a recumbent bike done slowly on low resistance? Of course you could lift weights for your upper body, and if you can tolerate it, walk slowly and build up stamina.
I would think your physical therapist should be able to help you with a program that would fit your needs.
But I think most importantly, you just have to do something. If that means walking for ten minutes, then walk for ten minutes. The more you do, the more you will be able to do. And of course get your diet right. Do that and you should be well on your way. Just keep on going! You can come back better than before. I mean, just think: one of your knees is completely new!