About 53 million U.S. adults are diagnosed with arthritis. How is arthritis diagnosed? Why and when does it usually arise? And what are the options available? We spoke with Robert McLean, MD, rheumatologist and member of the clinical faculty of the Yale School of Medicine, about the common types and symptoms of arthritis, from rheumatoid to psoriatic, various treatment options available, and the recommended lifestyle interventions to ease arthritis pain.