Is he developing osteoarthritis? OA runs cycles of flairs when the pain is bad and then it's ok other times. He might just need some doggie NSAIDs for when it flairs.
Really only happens if he runs too much (if thats possible). I do give him Cosequin dx as a supplement each day, hoping to stave off future issues. Also do have some Doggie pain pill for when I really see him hurting.