What Is Arthritis?

The word arthritis literally means joint inflammation, but is often used to refer to a group of more than 100 rheumatic diseases that can cause pain, stiffness, and swelling in the joints. These diseases may affect not only the joints but also other parts of the body, including important supporting structures such as muscles, bones, tendons, and ligaments, as well as some internal organs. This fact sheet focuses on pain caused by two of the most common forms of arthritis--osteoarthritis and rheumatoid arthritis.

What Is Pain?

Pain is the body’s warning system, alerting you that something is wrong. The International Association for the Study of Pain defines it as an unpleasant experience associated with actual or potential tissue damage to a person’s body. Specialized nervous system cells (neurons) that transmit pain signals are found throughout the skin and other body tissues. These cells respond to things such as injury or tissue damage. For example, when a harmful agent such as a sharp knife comes in contact with your skin, chemical signals travel from neurons in the skin through nerves in the spinal cord to your brain, where they are interpreted as pain.

Most forms of arthritis are associated with pain that can be divided into two general categories: acute and chronic. Acute pain is temporary. It can last a few seconds or longer but wanes as healing occurs. Some examples of things that cause acute pain include burns, cuts, and fractures. Chronic pain, such as that seen in people with osteoarthritis and rheumatoid arthritis, ranges from mild to severe and can last a lifetime.