It often helps to shorten the toes on the hind feet--not over-shortened, but don't let the hind feet (toes especially) get long. I've known a number of horses that were popping & then when their feet were trimmed so that the toes were shorter the popping stopped. If you do a search on here of "popping hocks" you should find a couple of old threads on the subject.
I had a young (2 year old) gelding that was popping on one hock for awhile, but he did outgrow it. He's 3 1/2 now & I haven't heard that hock make any noise in over a year now.
I can't say about your horse, but in many horses the snapping noise does originate in the hock; I've watched several horses that do this, and in some of them I could see the hock joint almost catch, then as it makes the snapping noise I could see the snap as something in the hock moved...didn't seem painful for the horses at all, but it did look like it should be uncomfortable. In other of the horses I didn't see that snap in the hock--those horses looked more like the ligament allowed the hock joint to move too far forward, then it would kind of settle back into place. In those I can't honestly say if the noise was actually in the hock (owner said it was) or in the stifle joint. In some cases (not all) I'd see that the snapping hocks went hand in hand with a weak/straight stifle.
I do know that many judges don't count a horse down for having popping hocks, and many trainers and buyers don't seem concerned by the trait; I know someone that's had a couple horses with the trait & when he mentioned it to prospective buyers, they couldn't seem to care less. That kind of surprises me; I personally prefer that my horses not have this trait, regardless if they are halter or harness horses. I always have to wonder how long a horse will stay sound if he's got this unusual catch in his hocks, but there are a number of people that say they've got horses that have done this for years & even with a lot of driving haven't had any soundness issues.
Edited to add; I doubt that there is any benefit in wrapping your horse's hock(s). The glucosamine won't hurt and may even help; do try shortening his hind toes a bit though, and see if that makes a difference.
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