We give ours Dasuquin, covers the spectrum of a few things mentioned above.
Amazon.com: Nutramax 150 Count Dasuquin with MSM Soft Chews for Large Dogs: Pet Supplies
We also walk them daily, limit their jumping up and down from anything higher than a couple steps. Have a ramp to go in and out of the back of the truck.
Another thing to look into is a Dog's bed. There are some really good beds for dogs that will help with these types of issues.