Arthritis is the most common cause of disability among U.S. adults and is particularly common among persons with multiple chronic conditions. In 2003, arthritis in the United States resulted in an estimated $128 billion in medical-care costs and lost earnings. To update previous U.S. estimates of the prevalence of doctor-diagnosed arthritis and arthritis-attributable activity limitation (AAAL), CDC analyzed 2010-2012 data from the National Health Interview Survey (NHIS). This report summarizes the results of that analysis, which found that 52.5 million (22.7%) of adults aged ≥18 years had self-reported doctor-diagnosed arthritis, and 22.7 million (9.8%, or 43.2% of those with arthritis) reported AAAL, matching and exceeding previous projected increases, respectively. Among persons with heart disease, diabetes, and obesity, the prevalences of doctor-diagnosed arthritis were 49.0%, 47.3%, and 31.2%, respectively; the prevalences of AAAL among persons with these specific conditions were 26.8%, 25.7%, and 15.2%, respectively. Greater use of evidence-based interventions, such as chronic disease self-management education and physical activity interventions that have been proven to reduce pain and improve quality-of-life among adults with chronic diseases might help reduce the personal and societal burden of arthritis.