So sorry that Harley is suffering right now! Have you been to your vet to find out alternatives to the Rimadyl and Tramadol??
Also, have you ever considered going to a holistic vet? We use one, and she basically integrates the best of western medicine with the best of eastern medicine so that we get the best of both worlds. I have a friend who goes to her for her bouvier which has very bad arthritis. They use herbal treatments, a nutritional supplement and some acupuncture and he's like a different dog.