vita flex 4000, its a glucosamine/msm/chondroitin supp dosed for horses. I got it from a feed store at $32/quart. I take 1-2 tablespoons a day. I've had it a month and a half and still have 3/4 of the bottle left. It works pretty well.
I will second the higher fat diet as well.
Edit: I do not take a horse sized dose of this stuff...
730/500/670 - 1900 @ 275