You might also check the animal and pet forum //www.curezone.org/forums/search.asp?f=88&q=arthritis+in+dogs&action=Search+...
Some posts they mention Innova food but that company has been sold and it is not on the "good" list anymore.
I usually give my 50lbs dog about 3 drops of Lugol's 5% a
week. On other days vitamin C and 1 Brazil nut a day. I make small pieces by cracking it in my mouth, so she won't swallow the whole nut.