I tried my dog on this when she first became arthritic, but didn't notice much effect. I guess all dogs are different!
What really helped her was hydrotherapy - I took her weekly for a few months, and then monthly, and she really responded well. It helped prevent muscle loss by allowing her to exercise without pain, which in turn improved her mobility.
She's too old to cope with hydrotherapy now (at 17.5 years) but still enjoys the shower jet being played on her hips and spine - not as a bath, just as a kind of massage - and of course I can do this at home whenever she looks uncomfortable. If your dog likes water it might be worth trying - I do keep her warm afterwards so she doesn't get chilled.