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.
Signs of OA are often times non-specific and include:
- Activity impairment: reluctance to exercise, decrease in overall activity, stiffness, lameness, inability to jump, changes in gait such as ‘bunny-hoping’.
- Pain on manipulation: behavioral changes such as aggression or signs of discomfort.
Diagnosis of OA is usually made by a combination of physical exam and imaging modalities such as X-rays.
- Initially physical exam will orient towards the affected joint or joints. The veterinarian will palpate the limbs and joints to assess for painful response, thickening of joint capsule, accumulation of joint fluid (effusion) or sometimes osteophytes and muscle atrophy (wasting).
- The most common imaging modality used is X-ray. These are of limited use though, because they only give information on bony changes (osteophytosis) and show only limited soft tissue changes therefore should be combined with physical exam findings.
- Other diagnostic tools becoming more popular include magnetic resonance imaging (MRI) which can provide information regarding soft tissue structures (ligaments, menisci) and computed tomography (CT) that is good for assessing bony changes in joints with more complex anatomy such as elbows, carpi (wrists) or tarsi (ankles).
Unfortunately OA is a progressive disease and continues to worsen with time. The conservative approach can slow down the progression of disease and many dogs can live comfortably for years following diagnosis. If surgery is performed the recovery of those dogs is usually very good especially with total joint replacement surgery as the diseased joint is completely removed and replaced.