I would contact your doctor to see what he or she thinks is best. They will almost certainly be on the conservative side. Most upper body training should be relatively safe. Most gyms don’t have it, but a Nu-step machine can allow you to exercise the non-affected leg if you are careful and creative with the setup.
Above all, I would watch what you are eating. That is the easiest way to make sure you won’t gain weight during periods of inactivity.