Osteoarthritis in the Sporting Dog, Part I
The lean white and lemon pointer soared across the Canadian prairie searching for that mesmerizing fragrance of chicken. Her gait was elegance-in-motion as she rolled across the wheat stubble with her massive muscles quivering and bulging…the shadows lengthening across the cold prairie and orange hues slowly fading to grays across the September horizon. As she rounds the corner on the last quarter section, I notice a very subtle change in her gait… “Danged burrs” was my very first thought! Or, is it possible that my 3 ½ year old, well conditioned, raw-boned, bird dog is developing osteoarthritis?
How is it possible that my pointer bitch is developing osteoarthritis at such a young age? Excellent question! Recent accounts in the literature suggest that approximately twenty percent of all dogs over the age of one already have some minor degeneration of their joints. Twenty percent of all dogs over the age of one…this makes osteoarthritis a significant sporting dog disorder. Having said that, what is canine osteoarthritis? Having a general knowledge of canine joint anatomy and the pathophysiology of osteoarthritis can be a benefit in the prevention and treatment of the disease in our canine partners.
Osteoarthritis (OA) is a slow progressive, wear-and-tear joint disease associated with the freely movable (synovial) joints within the canine body. OA is associated with a low-grade, chronic, inflammatory process within these movable joints that is coupled with the long term stresses of running and the effects of aging. Another way to envision canine OA is when the destruction of the joint’s structures (such as cartilage) exceeds the production, creating varying degrees of pain and discomfort to our esteemed bird dogs.
The canine skeletal system consists of numerous, separate, long bones that are fastened together by connective tissue creating an articulation or joint. A synovial joint is a freely movable joint that has a space between the two articulating bones. The synovial joint is comprised of a fibrous
capsule surrounding the joint and a very thin layer called the synovial membrane. The synovial membrane is very important in the load-bearing capacity of the joint because it produces the viscous fluid found in the joint that helps with the frictionless motion of the joint. Joint fluid or synovial fluid produces nutrients for the articular cartilage which covers the ends of the bones. Finally, the tendons, ligaments and muscles help provide flexibility and support to the synovial joint.
Athletic stresses or repetitive trauma to the joint can lead to injury of the cartilage cells releasing mediators (chemical enzymes that lead to destruction of the joint) of inflammation. These mediators cause damage directly to the joint by decreasing the viscosity of the joint fluid and causing death to the cartilage cells that protect the ends of the bones. Over time, inflammation results in the thickening of the fibrous joint capsule, formation of bone spurs, decreased joint flexibility, and painful swelling. The degree of discomfort caused by OA, to our athletic dogs, can be mild to performance stopping. In Part 2 of Osteoarthritis in the Sporting Dog, we will concentrate in great detail on the prevention and treatment of OA.