Not for arthritis but my Border Collie has had it for a couple injuries. He had weekly laser treatments for his iliopsoas pull, and then had a laser treatment on a pulled/sore triceps muscle last month. It's one of those things that it's hard to tell if it helped, because it was just one part of a treatment plan, but I trust the vets he's seen, and they feel that they have good success with the laser.
I'd certainly try it for arthritis in my dog, see if it helps. Acupuncture is something else I see recommended for arthritis, though I've never had it done on my own dogs.
Good luck with your boy!