I had a 17hh Hanoverian, with DJD, he was on a low maintenance dose of bute, which was increased for riding days; in an attempt to reduce the level of bute, we tried a variety of treatments including a number of supplements as well as a "Devils Claw" etc.
The most effective we found was to ride turn him out after riding in boots with magnetic inserts in them, it really seemed to make a difference to his comfort, we would only have them on for a limited period each day and take care to wash them, but they made him much more comfortable.
As an aside, I used a magnetic bracelet on myself, which helped me with a chronic sore spot on my foot that had, had me limping for two years, and been written off by the doctor as, non specific tendernous! (Very helpful!), within three weeks it had gone, it may be coincidence, but I'd try it.
When I was buying for Daisy I went for the band rather than the boots as she could have it on for 24hours a day rather than the boots that could only be worn for limited periods. That seemed to make more sense to me but it depends on what you're looking for.