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Questions and Answers about Arthritis Pain

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.

How Many Americans Suffer from Arthritis Pain?

Chronic pain is a major health problem in the United States and is one of the most weakening effects of arthritis. More than 40 million Americans suffer from some form of arthritis, and many have chronic pain that limits daily activity. Osteoarthritis is by far the most common form of arthritis, affecting about 16 million Americans, while rheumatoid arthritis, which affects about 2.1 million Americans, is the most crippling form of the disease.

What Causes Arthritis Pain? Why Is It So Variable?

The pain of arthritis may come from different sources. These may include inflammation of the synovial membrane (tissue that lines the joints), the tendons, or the ligaments; muscle strain; and fatigue. A combination of these factors contributes to the intensity of the pain.

The pain of arthritis varies greatly from person to person, for reasons that doctors do not yet understand completely. Factors that contribute to the pain include swelling within the joint, the amount of heat or redness present, or damage that has occurred within the joint. In addition, activities affect pain differently so that some patients note pain in their joints after first getting out of bed in the morning whereas others develop pain after prolonged use of the joint. Each individual has a different threshold and tolerance for pain, often affected by both physical and emotional factors. These can include depression, anxiety, and even hypersensitivity at the affected sites due to inflammation and tissue injury. This increased sensitivity appears to affect the amount of pain perceived by the individual.

WebMD Public Information from the U.S. National Institutes of Health

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