I fortunately have not had any problems with HD in any of my dogs- god willing, it will never be an issue. If you are happy and content with your vet, talk to them- find out what else you can do- what the other options are. If not, find another vet. Anytime you have a dog that has an on going problem, you need to have a vet that you trust and can rely on to do what is best. Find out if your vet has a lot of experience with HD and large dogs, again if not, you may want to find one who has had that experience. Your poor Lexi, I am thinking that going for walks is not in her best interest right now- at least not long ones. Keep us posted with how she is doing.