Osteoarthritis (OA) is the most common joint disorder diagnosed in dogs.1 OA is a term used to describe the process of joint cartilage degeneration. It is a chronic, progressive, and inflammatory disorder that results in articular cartilage damage as well as degenerative and proliferative changes in the joint. Normal joint cartilage is composed of collagen and protein matrix that are produced, assembled, and maintained by a relatively small number of chondrocytes. Damage to articular cartilage may result from abnormal mechanical stress on the joint or an idiopathic phenomenon. These abnormal stresses can include congenital deformities, abnormal conformation, or trauma. Disruption to the normal articular surface or joint instability can alter the normal wear pattern of joint cartilage and increase the turnover rate of the articular matrix. Even though this process is largely inflammatory in nature, it is accelerated by cytokines and prostaglandins released by synovial cells into the joint. The joint capsule then proceeds to thicken and periarticular osteophytes form in the body’s attempt to stabilize the joint.
OA is an insidious disease that can affect one or multiple joints. Initial clinical signs such as lameness and stiffness may only be evident after periods of overexertion or may worsen in cold and damp weather. Dogs with milder forms of the disease will have their owners report that their dog “warms out” of their lameness with mild exercise. As OA progresses, joint function is lost due to fibrosis and pain, which in turn leads to exercise intolerance, profound lameness, and in severe cases, muscle atrophy.
OA is diagnosed based on patient signalment, history, physical examination, and radiographs. Clinical examination may reveal a combination of the following: pain on palpation of the affected joint, decreased range of motion, crepitus, and joint swelling. Radiographic changes can include subchondral bone sclerosis, subchondral cyst formation, joint space narrowing, and periarticular osteophyte formation. Radiographs may also reveal a predisposing condition such as trauma, rupture of supporting ligaments, poor joint conformation, or congenital deformity.
The goals for treatment of OA include prevention of further cartilage degeneration and pain control. Weight reduction may decrease stresses acting on the joint. Rest during the initial stages of therapy can help to decrease discomfort. Low impact exercise such as swimming and short leash walks should be done in moderation once initial pain control has been established to maintain the dog’s strength and mobility. Pharmacologic and non-pharmacologic therapies may be used to decrease further cartilage degradation, inhibit the release of inflammatory mediators, and control pain.
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- Epstein M, Rodan I, Griffenhage G, et al. 2015 AAHA/AAFP pain management guidelines for dogs and cats. J Am Anim Hosp Assoc. 2015; 51:67-84.10.5326/JAAHA-MS-7331
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