Osteoarthritis (OA) is a nearly universal, slowly progressive degenerative condition affecting men and women as they age. OA of the hip and knee represent two of the most significant causes of pain and physical disability in adults. In the United States, OA is the second most common form of disability, and although it affects both men and women, women are more likely to be symptomatic. Despite its prevalence, OA is not necessarily an inevitable consequence of aging. Many advances have been made in understanding the pathophysiology and epidemiology of OA, and these advances are helping to dispel such attitudes. Evolving recognition of predisposing risk factors and pathophysiology suggest prudent steps that can be recommended. This article provides information for caretakers that will help them understand the disease process and plan appropriate therapeutic interventions.