What's Rheumatoid Arthritis?Rheumatoid arthritis is an umbrella term for more than 100 different diseases. It is a disorder of the locomotor system. These are joints, muscles, tendons and bones that help you move. In rheumatoid arthritis, the body's immune system is inconsistent, which can lead to chronic inflammation. Almost all forms of rheumatoid arthritis cause pain and stiffness in the joints and muscles. Millions of people suffer from rheumatoid, mostly older people. This disease often develops as you get older. Many of these people live with daily pain, stiffness and fatigue because of their rheumatoid arthritis. Many forms of this disease can be treated, but it is not yet completely curable. Many people do not realize that they have rheumatoid arthritis because it is on the inside of the body and because they experience mild symptoms.