Arthritis - Causes

The causes of both rheumatoid arthritis and osteoarthritis are not known. At one time, doctors believed that OA was simply a part of growing old. They thought that the body's joints just wore out over time. Today, researchers are beginning to explore specific causes for both disorders.

Rheumatoid Arthritis

Current theories suggest that RA is caused by genetic factors. That is, a person is born with the tendency to develop or not develop the condition. Then something in the environment actually sets off the disorder itself. One theory is that an infectious agent, such as a bacterium or virus, initiates the onset (beginning) of RA.

Whatever the cause, RA is an autoimmune disorder. An autoimmune disorder is a condition in which the body's immune system begins to act abnormally. The immune system is a network of organs, tissues, cells, and chemicals whose job it is to protect the body from foreign invaders, like bacteria and viruses.

At times, the immune system may become confused. It may respond to some part of the body as if it were a foreign invader. It releases its whole arsenal of weapons against that part of the body. When the immune system acts against some part of the joint, RA occurs.


Scientists recognize two forms of OA: primary and secondary osteoarthritis. Primary OA is caused by abnormal stresses on healthy joints or by normal stresses on weakened joints. The joints most commonly affected by primary OA include the finger joints, hips and knees, the lower joints of the spine, and the big toe.

There is some evidence that primary OA is caused by genetic factors. Obesity is often a contributing factor. The heavier a person is, the greater the pressure on his or her joints. Finally, some researchers believe that primary OA may be caused by bone disease, liver problems, or other abnormal conditions in the body.

Throughout history, gout has been called the "disease of kings." The reason for this name is that gout can be caused by the over consumption of rich foods. Today, we know that gout is caused by the accumulation of uric (pronounced YER-ik) acid crystals in a joint, most often the joint of the big toe.

Uric acid is produced in the body when proteins are broken down. Proteins are a class of chemicals with many important functions in the body. Uric acid is water soluble. It usually dissolves in urine and is then excreted from the body.

Some people, however, produce an unusually large amount of uric acid. Such a tendency is thought to be caused by genetic factors. When that happens, uric acid remains in the body, circulating through the bloodstream. Eventually, it is deposited as needle-like crystals in joints. These crystals cause friction when the joint is moved. The friction causes severe pain known as gout.

Secondary OA is caused by a chronic (long-term) or sudden injury to a joint. Some factors that may contribute to the development of OA include:

  • Physical trauma (shock), including sports injuries
  • Repetitive stress associated with certain occupations, such as construction, assembly line work, computer keyboard operation, and hair-cutting
  • Repeated episodes of gout or other forms of arthritis
  • Poor posture or bone alignment caused by abnormal body development

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