ACL/MCL/Lat. Meniscus/Bone Bruise playing Ultimate Frisbee

I'm a 20 year old college student who plays ultimate frisbee. A few weeks ago, I twisted my knee when my left cleat stayed in the ground while I turned my body to start cutting. There was a loud crack and unbearable pain as I hit the deck, and I knew immediately that it was an ACL injury. The year before, I had damage to the MCL on my other knee and did a fair amount of research on knee injuries, so I knew immediately it would be the ACL. The best analogy I can use is twisting open a cap of a new bottle of soda: I imagine all the ligaments inside my knee twisted off in the same way.

I've been worrying about damage to the meniscus and the bone bruise, because I hear that they can lead to premature arthritis. The meniscus is apparently not all that bad, but there's nothing I can do about the bone bruise. I don't want a life full of pain, and I don't want to be afraid to be active again (even to run, I'm afraid the pounding on the cartilage will wear it down faster), but I don't see any alternative. Anyone have any input or advice?

I'm having surgery in two weeks, which will be a month after injury. After having the knee drained a week ago since the swelling wouldn't go down, I can somewhat extend and flex to 90 degrees. But I can't walking with the knee entirely extended at 0 degrees, and I hear it has to be before surgery or else it won't ever be able to straighten totally. True, if so, any suggestions to help me walk normally again? I also feel a lot of pain when I try to bend past 90 degrees, and although I'm keeping at it, I don't know if it'll get better in time.

What types of exercises have you all done pre-op and also post-op, and did you all get total ROM back before going into surgery? Thanks!