Once you're a little more able to get out you You can work on a rowing machine strapping in your good leg. As for weight training if you're worried about putting on weight then you should set a timeframe for your exercises and work in a circuit not doing the same exercise 2 sets in a row, this'll do more than just high reps work alone. Better than high reps is find out how much repetitions that you can do for a particular exercise in 30-60 seconds and improve on that. Circuit training can be high intensity and a lot of guys have been doing a form of it in one way or another. Your doctor has probably told you to avoid any weight bearing exercise for that movement, but other than that you should be able to work on other things as long as you're careful.