Arthritis:

Bones, cartilage and ligaments provide the body with the scaffolding necessary to have four fully functional legs, provide protection to the internal organs, and facilitate the full range of motion.  Regardless of how much muscle an animal has, without the support of healthy bones, joints and connective tissues, appropriate function is not possible.25  Joints enable an animal to be flexible when walking, jogging, running, jumping or climbing.  Synovial fluid coats joints and facilitates smooth movement.  As joints age or are damaged by injury or disease, arthritis can occur.28

There are two primary types of arthritis, degenerative and inflammatory, depending on the source of inflammation.  Degenerative joint disease (osteoarthritis) occurs when cartilage that protects the joint is damaged, either from normal stress on abnormal joints (ie. hip dysplasia), or abnormal stress on normal joints (i.e., jumping or falls). The second type of arthritis is inflammatory joint disease, which results from infection or from underlying immune-mediated diseases.²⁸  With age or upon joint insult, the hyaluronan in synovial fluid breaks down and becomes thin and watery, reducing its ability to provide lubrication and shock absorption,²⁹ resulting in osteoarthritis.