1. Glucosamine, chondroitin, and MSM. This stuff was developed for greyhounds and it works well for people, too. I take 4 pills a day, give the dog one.

https://www.swansonvitamins.com/swanson-premium-glucosamine-chondroitin-msm-500-400-200-mg-240-tabs

2. Linseed oil. Put a couple tablespoons of it on his food every day.