You CAN stay in shape while recovering from injury. As long as you're cleared with by your doctor and the moves have been approved, there's no reason you can't work the other pieces of your body that are ok. I tore my ACL and both meniscus and had a complete repair 5 months ago to this date. I was on crutches for a month, and in a brace for 6 weeks with no bending past 90 degrees for that entire time. The video was shot in Novemeber but edited/posted in January. The only muscle I lost was in that left leg, which I am continueing to rehab and rebuild daily. People were astonished to see me back at the gym (2 weeks after surgery) and surprised that my body didn't change throughtout my whole ordeal. I did lose weight and muscle right after surgery (not a lot of moving or eating) but once I felt better I was up and going. I started out slowly with just home workouts but 14 days later I was back at the gym. I just didn't see the point in losing the physique I'd worked so hard for, for so many years in a matter of months, especially when I was perfectly capable of working out.
I hope these workouts help you keep moving not just for your physical state, but your emotional state as well.
Check out---> Leg-less Workout Upper Body
Also check out my--->> Footless Workout
This workout was created after I broke my foot competing on American Ninja Warrior. Read about that here --> American Ninja Warrior after my Injury