Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you today.
First, I would note that Rimadyl is often a treatment of choice for these situations. If it hasn't helped your lad, then I would advise speaking to his vet at this point to try an alternative (ie Metacam, Onsior, Previcox) that may work better. Or if you think there is still a pain element here, then he could also be treated with Tramadol, Bupenorphine, or Gabapentin.
Otherwise, we'd want to consider potentially using joint support/supplements alongside medical management. In regards ***** ***** we can help your lad, if he is not on any joint supportive treatments already, I would suggest that you could consider starting him on glucosamine/chondroitin supplementation. This can be helpful for some dogs with arthritis and just get them moving better. This is a nutrient supplement that is available at your vets, pet shops, and health food stores (as capsules, liquids, and even treats). There are a range of products on the markets and the ones we typically use for dogs in this situation would be Cosequin, Seraquin, and Flexivet. It works by aiding joint suppleness by helping cartilage replenish itself and blocking enzyme destruction of cartilage in the joint. Often we can find this helpful in animals with mild signs but can be of benefit for more severe cases too. Normally we give dogs 300mg glucosamine + 50mg chondroitin a day per 10 pounds of body weight. So this would be something to consider for him.
Further to this, you can also consider treating him with fish oil (omega 3 or 6; EPA/DHA). These too can be helpful as they do have anti-inflammatory properties and can reduce joint discomfort and weakness too. In regards ***** ***** we tend to give this at a rate of 20mg per pound of their body weight. So, this too would be a consider here for your lad. As well, there are other treatments like Duralactin or Catrophen that could be worth discussing with his vet. And finally, just to note in case your vet has seen signs of nerve degeneration when he was examined, then steroids may also be an option here.
Overall, if the Rimadyl has not helped, then we need to trial an alternative since some work better for individuals then others. Otherwise, I would advise adding in the above to help his overall joint health/strength to see if we can keep him moving comfortably for as long a posisble.
Please take care,