Without knowing the exact diagnosis and why she is not able to walk now , it would be very dangerous to recommend physiotherapy. If you have not done so yet, Lucy needs to be seen by a veterinarian and the cause of the paralysis needs to be found, whether it is a fracture or pinched or damaged nerves or a slipped disk caused by the accident. This exam by your vet will also determine if there is any hope at all for your dog to be able to regain movement in his hind legs. Physical therapy can actually damage your dog more, if there are certain nerves or fractures involved.