My ZZ (100 lb. Rottie) is only 4 years old, but had elbow displaysia that we missed while busy treating her mal-formed bladder and torn cruciate ligaments... If Bonnie ( 60 lb. SP) needed all this, which she does not, I would cut the doses in half. Here is what I give her for her Stage 3 (the worst) arthritis:
Glucosamine Sulfate or liquid Glucosamine are the best absorbed -- credit for this info goes to Susan F. and ZZ seems to be getting a little better -- or rather has more good days on Glyco-Flex III.
On her food, she gets: 1 Tbl. Apple Cider Vinegar + 1 Tbl. good expeller or cold pressed oil (my favorite is Grape Seed Oil or Olive Oil.) This is excellent for cleansing the system, and that also will help the arthritis tremendously. I think it probably helps with a lot more as well. ACV is an old-time remedy and they used to take it straight from the tablespoon! I've read with interest the comments that it might help with eye staining... Interestingly, my acupuncturist tells me that the more alkaline the system, the less the pain you will experience from something like arthritis.
Also, check for food or environmental allergies also with Arthritis. Food allergies can lead to some impressive muscle and joint pain. Also, a magnesium deficiency can contribute muscle pain. If you decide to give magnesium, you need to combine it with calcium, zinc and D.
Take care and let me know if I can help or look anything up for you!
* I don't give the Vitamin C daily though as Bonnie doesn't like it on her ground chicken or turkey. She has no problem with it on fish, beef or lamb! ZZ will eat anything that won't eat her first! Both of my girls will also eat chewable Vitamin C -- orange or raspberry flavored!