Osteoarthritis (OA) is the most common form of arthritis affecting companion animals. In the United States with an approximate dog population of 44 million, published data indicate that as many as one in five or 20% of the adult dogs suffer from some degree of OA. Cats frequently suffer from OA as well. Osteoarthritis is a degenerative process, sometimes referred to as “degenerative joint disease” (DJD), and is exhibited by progressive destruction or loss of the cartilage surface in the affected joint(s).
Osteoarthritis typically develops as a consequence of: development disorders, articular trauma or acquired orthopedic conditions. Other causes for arthritis include
immune-mediated and infectious processes. Osteoarthritis develops slowly and progressively. Once the process has been set in motion, it is difficult to arrest and impossible to reverse. As the environment of the joint changes with the development of OA, alterations occur in the basic properties of the articular cartilage. As these changes occur and progress, the cartilage is no longer able to provide pain-free movement in the affected joint(s). Patients with OA thus typically develop stiff and painful joints.
Diagnosis of OA begins with a thorough patient history and physical exam. Owners often report a specific lameness or distinct behavioral change. Earlier symptoms may be more subtle. Physical exam findings typically include: muscle atrophy (wasting) in the area of the affected joint, joint stiffness (loss in the range of motion) and tenderness with manipulation, increased joint fluid (effusion) and increased thickness or swelling (periarticular fibrosis) around the affected joint. Currently, radiographs (x-rays) constitute the primary method of definitive diagnosis. Radiographic changes, however, occur later in the disease process and do not necessarily correlate with symptoms. As we say, “dogs do not walk on their x-rays.” This implies that patients with significant OA, as noted on x-rays, may have significant joint pain. Whereas patients with minimal OA, as documented on x-rays, may have significant joint pain. Furthermore, x-rays may document that a patient has OA in more than one joint of a lame leg (i.e. hip and knee) again stressing the importance of a thorough exam to determine which joint(s) is/are painful and responsible for the lameness.
Treatment of OA depends to a large degree on what stage the disease process is in at the time of initial diagnosis. In every case, however, a multi-modality and/or multi-agent therapy is advised. Ideally, medications for OA would relieve pain and inflammation, retard on-going joint degradation and promote joint tissue healing. No single ideal medication exists for OA treatment. A typical multi-modality approach to treatment OA involves the following: weight reduction, an exercise program, anti-inflammatory agents, chondroprotective agents (nutraceuticals and DMOADs), narcotic analgesics, ancillary modalities and surgical intervention (if indicated).