If you suffer from aching, stiffness, and swelling in and around your joints, you very likely have arthritis and you re in good company. In fact, an estimated 23 percent of all American adults over 54 million people have arthritis, according to the Centers for Disease Control and Prevention (CDC). There are many different types of arthritis, with the most common form being osteoarthritis, which begins with gradual wearing down of the cartilage surfaces between the bones that make up the joint, explains Jason Kart, P.T., D.P.T., the owner and physical therapist at Core Physical Therapy The Loop in Chicago. The cartilage acts as a cushion between the bones, but as the cartilage breaks down, more stress is transferred to the bones underneath it. Over time, the bone starts to degenerate which leads to joint swelling and pain.