my sister's 15 year old dog had such good results with this that in 2 days he became like a puppy again: SYNFLEX: http://www.syn-flex.ca/allaboutglucosamine.html
liquid is the best form and best absorption, don't bother with tablet ones, they don't work.
make sure to get liquid is the best form. Synflex gives you exact measuring cup and instructions. But if your dog is picky like my sister's dog, she had to give her dog ARTHRIX because she could hide it in his food easier.
ALSO, IN ADDITION TO THE GLUCOSAMINE: TRY THE HOMEOPATHIC REMEDY FOR ARTHRITIS: clear, odorless, tasteless, use 4-6 drops in 2 cups of water, just put in their water dish. http://www.pets4homeopathy.com/remedies.html scroll down on that page and see Arthritis - THEY ALSO HAVE ONE FOR JOINT RELIEF. Joint Disease
Muscle, Joint, Arthritis Reliever - Formerly known as Arthritis Reliever KB (please see description of this product) Many horses find relief with this.
LiverDetox or Pet Detox
Sciatica Relief (if nerve pain accompanies)
K9-Level 5000!! [see products page]