Osteoarthritis (OA) in dogs is a degenerative joint disease characterized by the breakdown of cartilage, leading to pain, inflammation, and reduced mobility. It commonly affects older dogs but can also occur in younger animals due to factors like genetics, obesity, joint injuries, or developmental conditions such as hip dysplasia. Symptoms include stiffness (especially after rest), limping, difficulty rising or climbing stairs, reluctance to exercise, and visible joint swelling.