With foot/ankle injuries, always get a knee scooter in addition to ergonomic crutches, the kind with spring tips. I was NWB for more than two years total after seven lower-limb surgeries. Ask your surgeon if you can lie on your back, feet in the air, to do range-of-motion exercises for your legs, knees, groin, hips and IT bands. Ask for guidance on the gastrocnemius in particular.
@Herbaceous, has the doctor proposed an ultrasonic bone stimulator? And are you pounding calcium and Vitamin D?