O steoarthritis is a progressively painful disease characterized by articular cartilage degradation with loss of proteoglycan and collagen, subchondral bone sclerosis, periarticular proliferation of new bone, and chronic inflammation of synovial membranes. 1 Osteoarthritis is estimated to affect approximately 20% of dogs ≥ 1 year of age and 90% of dogs > 5 years of age. [2][3][4][5] Cats are similarly affected by osteoarthritis, with prevalences ranging from 16.5% to 91% and increasing with age. [6][7][8][9] Given the high prevalences reported, it is possible that companion animals may have undiagnosed osteoarthritis and the associated pain that goes unnoticed. Cats in particular may not show clinical signs typically associated with osteoarthritis, and even subtle changes in a cat's behavior at home may be caused by osteoarthritis-associated pain. Veterinarians should closely evaluate patients' joints at every annual examination and discuss signs of osteoarthritis and pain with clients. To prevent disease progression as early as possible, discussions about osteoarthritis should take place for patients as young as 1 year of age. Careful evaluation and client education are essential to identifying osteoarthritis in its earliest stages.Clinical signs of osteoarthritis include evidence of pain or tenderness, decreased range of motion, swelling, stiffness, muscle atrophy, crepitus, and effusion. The presence of pain can cause an animal's behavior to change, leading to aggression or decreased activity, in addition to signs such as limping and difficulty rising, climbing stairs, or getting onto furniture. 10 Painful disease makes it difficult for pets to interact with people, which strains the human-animal bond and can damage the relationship with the owner. Because of osteoarthritis-related pain, pets may have trouble walking around the home. They