Old fat and slow,
Dude, seriously, you are about 12 weeks away from being lean and fit.
Anyone who doesn't have much fat to lose can do a 12-week program and come out looking much different.
Power 90
P90X
Insanity (that one isn't even 12 weeks - just 60 days, but it might be too much for you)
Or just find some dumbbell workouts on Youtube. Do these 3 days a week...find at least a 30-minute session, and go for max of ~50 minutes.
On cardio days, these types of programs would have you do punch and kick, run in place, hop, jumping jacks, etc., but if your injury makes you unable, I suggest you do the elliptical. You say you don't have one. Well, go BUY one. Just 3 days a week. You can stomach that 3 times a week.
MWF - weights
TTHS - Cardio
Sunday - OFF
Don't eat crap, drink water, do the exercises, sleep. You just have to DO it. Since you aren't even fat, you could be ripped at the end of 12 weeks.