Being immobile for 6 months, all muscles with atrophy.

When the vet recommends it, just starting out walking is good too.

I would ask about rom theraphy for now to keep things supple. Ask your vet if you can do that - ROM is range of motion exercises, much like we do when we got o physical therapy. Keeps muscles supple and stretched.

I would recommend water therapy for starters, just walking. I don't know if you have anyone around you, there are some therapy vans that travel around the country. If you have race tracks or race horse breeders around you - I would ask them if they have a therapist.

Remember patience would be key here.