If you’re one of the estimated 27 million Americans with osteoarthritis, you know what it’s like to live with stiff, swollen, and painful joints. Caused by the breakdown of bone-protective cartilage in your joints, osteoarthritis is the most common form of arthritis and typically affects the hands, knees, and hips. (Rheumatoid arthritis, which affects another 1.3 million Americans, is an autoimmune disorder that can also affect the heart and lungs.) Read next feature >