I'm an advocate of oral hyaluronic acid preps. The two products I am familiar with are Hyaflex (http://www.hyaflex.com/) and Hyalun (http://www.hyalun.com). Hyaflex is for small animals and Hyalun is originally for horses, but works great for larger dogs. Hyalun is just more concentrated (and has a longer shelf life). For example my puppy is getting 1/4 dropperful of Hyalun once daily, so at this rate the bottle will last 4 months!

I get the product from the vet. I think they are for sale online, but definitely keep an eye on expiration dates if you go that route. They are dated with little stickers stuck to bottom of the bottle - a poor design which can probably be easily tampered with. Sorry, I am pessimistic about online retailers when it comes to products that degrade and have expiration dates.

From the Hyalun site....
How does hyaluronic acid compare to glucosamine or chondroitin?
Glucosamine is a precursor of hyaluronic acid. Hyaluronic acid in turn makes the synovial fluid. Glucosamine must to combine with a glucoronic acid molecule to make hyaluronic acid. Often times the body is not able to join these two molecules together and the the production of the much needed hyaluronic acid is never achieved. By administering hyaluronic acid, you take away the risk of this integral process not happening and may see results with hyaluronic acid that you did not see with glucosamine or chondroitin.
For more serious joint issues, I would also recommend Adequan injections (another product originally designed for horses). We are offering them now at my clinic, and lots of our older dogs are seeing very marked improvement. These dogs have been on glucosamine/chondroitin long term prior to the Adequan. Many of them are also already getting regular acupuncture.

Adequan site: http://www.adequancanine.us

Okay, probably enough from me for now. If anyone wants to know more, feel free to PM me!