Well, if it helps at all, I have mild to moderate arthritis in both ankles and right knee. I've tried ALL the supplements you can think of and nothing really helps except painkillers (ibuprofen). Glucosamine and chondroitin were the first things I tried but found to be useless (confirmed by online research).
If any of these supplements really worked (for dogs or humans), we'd know about it (in the same way that Dermacton really works for skin problems).
I regularly take hooman salmon oil caps 'cos it can't do any harm. Omega 3 is good for joints too and I've found it helps with the occasional eczema flare up (I use Aniforte Omega 3 salmon oil for Jack mainly to keep his skin/coat healthy and glossy)
As for whether the Arthri Aid will help Ollie, I've got to be true to form and be a sceptical old f*rt, though much depends on the dog (as it does with humans). Personally, I'd save my money, continue with the salmon oil, take it easy and see how he goes.