Arthritis is a broad range of conditions that involve inflammation of one or more joints in the body. This inflammation results in decreased mobility, joint pain, joint stiffness and typically worsens with age. There are many kinds of arthritis, but the most common form is osteoarthritis and rheumatoid arthritis. Osteoarthritis is breakdown of cartilage (the slippery tissue that cushions joints). This causes decreased joint function, swelling and pain. Rheumatoid arthritis is an autoimmune disease in which the body actually attacks itself and leads to breakdown, inflammation and swelling in the joint linings.