The word arthritis is derived from the Greek words arth (“joint”) and itis (“inflammation”)—when your joints become inflamed. To humans, it can mean suffering from joint pain and stiffness. More than one hundred types of arthritis exist, some that affect the skin, muscles, bones, and internal organs as well as the joints. Another type of arthritis is rheumatoid arthritis, in which the joint pain is caused by the immune system’s attack on the membrane lining the joints. Together these types of arthritis are called rheumatic diseases, and they are considered to be one of the most common chronic health problems for humans.