Osteoarthritis (OA) is the most common form of arthritis in dogs affecting a quarter of the population. It is a chronic disease characterized by loss of articular cartilage that is covering and protecting the ends of bones in most joints of the body. In association, there are other abnormalities present that include new bone formation around the joint (osteophytosis) as a response to increased instability and inflammation in the joint leading to pain.
In contrast to humans, OA in dogs most commonly occurs secondarily due to developmental orthopedic disease (cranial cruciate ligament disease, hip dysplasia, elbow dysplasia). The joints most commonly affected are the hip, stifle, and elbow. The exception to this is idiopathic (unknown cause) OA of small joints of digits (manus and pes) that is seen in older dogs. Contributing factors to OA include genetics, age of dogs, bodyweight, obesity, gender, exercise and diet.