Sorry to hear that, man. As a physically active person, injuries have always been the worst. They put me in a state of depression unlike anything. So I feel for you, I do. If it's any consolation, you can still find ways to workout and stay relatively fit. First, get this:
You can absolutely do pull-ups. They're a fantastic workout, and you can maintain lots of upper-body strength by doing them every day.
In addition, you can probably do push-ups if you keep your leg elevated. Again, do them every day. Also, find a way to do dips (like between two chairs--just make sure you've got plenty of room for the descent and that they're sturdy), and you'll continue to develop strength and muscle everywhere but your legs. Which is unfortunate, but at least it's something, and when you return you can hop on a beginner strength program that has you squatting three times a week and before you know it your legs will be developed again.
Oh noooo! Well brother every day is upper body day now!
Thanks for the advice guys. Hopefully I won't lose too much. I already upped my protein intake to ensure I don't lose too much, while also keeping my calories under 1900/day.