There are natural agents called DMOAs or disease-modifying osteoarthritis agents that help dogs with osteoarthritis by improve the function of bone cartilage or fluid (synovial fluid, a fluid that lubricates the joints). These products include glucosamine (a substance the is naturally found in a dogs body) and Chondroitin sulfate (CS). Studies are inconsistent, with some showing improvement in relieving some arthritis symptoms in humans. Both are found in dog foods that promote joint health, although there are no studies that support their use at levels in food. There are also other ingredients that have some support for use.