i have lived with a dog with arthritis, and that Tramadol did seem to help Toby. I share Sara's general wish to avoid prescription meds, too, but, like her, if you got to, you got to.
I also used some chondrotin/glucosamine mixture, which i was never sure if it helped much or not. But i was desperate enough, i probably would have hired rain dancers, if someone said it might help.
One thing we tried to do for him, as often as we could, was get him in water, to swim a bit. There are some wonderful doggie life vests out there, for dogs who don't have much energy, makes swimming easier. If you don't have a nearby lake, your vet might know of a place where dogs can swim.
It was hard geting him into the SUV, so we built him a doggie ramp for that.
Tricks training might help him have as much joy as he can, if he is limited on other activities. Even dogs who can't move much, can learn some tricks. Really gives a dog a very very satisfied feeling, like they accomplished something, got a chance to use their minds, have a chance to please their owner and get praise for doing something, etc.
Maybe dogs, like humans, may even find distraction a good therapy, the way humans do...(?)
If you are interested in some tricks even dogs who can't move much, let us know, is great community here, who'd be real willing to help you learn some low-activity tricks, if you want to distract him....if you've never done it, you might smile hugely to see how much your dog loves doing tricks. Many tricks can be done lying down, too.
and it's not hard to do, either, only five or ten minutes a day, can teach a dog a trick.
BEST OF LUCK. I know you are doing all you can for this dog. And do let your vet know, if you feel the meds are not helping, in case he has anything else to offer.