Arthritis is the most common cause of disability among U.S. adults.1 Data from 2007 to 2009 show that one in five, or 50 million, U.S. adults reported doctor-diagnosed arthritis in that period; one in nine, or 21 million, had arthritis-attributable activity limitations.2 In 2003 the costs attributable to arthritis and other rheumatic conditions were $128 billion ($81 billion in medical expenditures and $47 billion in earnings losses), which represented nearly 1% of that year's U.S. gross domestic product.3 The number of U.S. adults with arthritis is projected to rise to 67 million by 2030.4