
All my dogs get salmon oil and if they are allergic to that coconut oil regardless of age. That will help prevent joint issues.
All my dogs get a glucosamine supplement from about 7 years old, again as a preventative.
The rest I just use what I feel works best, which might be different for each dog. Turmeric is great and works for many dogs. Two of mine are on it: one is 13 and he seems to be bouncier with turmeric in his diet which means he probably has some joint discomfort (although not really noticeable in every day life), and the other one gets it because he has degenerative disc disease and it means he doesn't have to be on conventional pain killers (yet).
It is just a matter of trial and error as to what works for your dog.