I have been going through studdies on Joint Suppliments, since Nelson injured his hock.
I have discussed orals with my Vets and they all stress that orals may, or may not work. They are not proven to be effective, nor are the containers all that truthfull about the contents and the amounts of the contents.
They say that IM Injections are the only proven route that is effective.
I found this great article and wanted to share it with you guys:
Veterinarywatch : Oral Joint Supplements
The Horse | Oral Joint Supplements: Do They Work?