What supplement works best for hoof and joints.?

My horse is only 7 almost 8 years old and has always had his back legs make a popping sound, but he never acted as if he was in pain. I rode him since he was 4 and as long as I remember he had this. His owner at that time seemed to not care, but I'm wondering now if I should start him on a joint supplement. To me this noise sounds weird and might mean when he is old he joints will get worse, even though now nothing is wrong when he gaits or runs. What do you guys think, what brands have you had success with, and is their one that works for joints and hoof together?