She begins, in the morning, by casing her joints: Can her ankles take the stairs? Will her fingers open a jar? Peel an orange? But it was not always this way for Mary Felstiner, who went to bed one night an active professional and healthy young mother, and woke the next morning literally out of joint. With wrists and elbows no longer working right, she'd discovered one of the first signs of rheumatoid arthritis, the most virulent form of a common...