It only has 20% protein and IMO that is not enough for a dog with arthritis (or any dog - I like at least 26%). You need protein to build and maintain muscle to aid in arthritis. Muscle supports bones, tendons, ligaments, joints. I don't like the ingredients either.
Here is more info and suggestions for natural things you may want to try. It often takes more than one supplement (holistic) to get results and you need to give them time to work.
Our Beloved Canine Seniors