Chondroitin sulfate, a common ingredient in joint supplements, is a type of glycosaminoglycan and is related to glucosamine, though it has not been studied as much as glucosamine has. It is often referred to simply as chondroitin. It is a natural component of a dog's cartilage and bones.
Joint supplements usually use chondroitin sulfate in conjunction with other ingredients believed to help relieve joint pain, such as glucosamine and methyl sulfonyl methane (MSM).
Chondroitin sulfate can be used to help manage osteoarthritis in dogs, since it is a component of the dog's cartilage and may help the cartilage rebuild or stop eroding.
Chondroitin sulfate is also an anti-inflammatory and helps to reduce pain, and, with other glycosaminoglycans, helps to regulate oxalates in the body. This may help to reduce kidney stones in dogs.
Chondroitin sulfate supplements fed to dogs are always made out of animal cartilage.
The majority of glycosaminoglycans found in dog's bones are chondroitin sulfate, so supplementing with chondroitin sulfate may help bones heal.