Look into laser therapy. Find a vet who offers it and give it a shot. May take a little bit of effort to find a vet who offers it around you because the lasers are extremely pricey. I only know of a few up here in Dallas.
You may also look into RVI injections. I would actually probably look into them before laser therapy. Both should help immensely though.
Found some people that do laser therapy close by, I'm gonna have to keep looking to find someone that does the RVI injections.