According to the Centers for Disease Control and Prevention (CDC), 46.4 million adults in the United States have doctor-diagnosed arthritis. That's a large number -- and it's growing as the population ages. What causes so many people to develop arthritis? Is arthritis contagious? Is arthritis a disease that can be transmitted from person to person?The short answer is no -- it's not contagious. You will do better learning about risk factors for arthritis when considering why so many people develop the condition.