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Home >> Arthritis   >>  Causes

Causes

What causes osteoarthritis?

Although the exact cause of OA is not known, some scientists believe that joint damage begins in response to physical stress (such as an injury or repetitive movement).

Also known as "wear and tear," this stress can erode the cartilage that normally encases the ends of the bones in a joint. Cartilage serves to cushion the bones and to help the joint move smoothly and easily.

As cartilage breaks down, the ends of the bones thicken and the joint may lose its normal shape. With further cartilage breakdown, the ends of the bones may begin to rub together causing pain. In addition, damaged joint tissue can cause the release of certain substances called prostaglandins, which can also contribute to the pain and swelling characteristic of the disease.

Factors that may increase your risk of developing OA include:

  • Age. Age is the strongest risk factor for OA. Although OA can start in young adulthood often due to joint injury it usually occurs in older people. By 2030, 20% of Americans' about 70 million people will be age 65 or older and will be at risk for OA.
  • Female gender. Before age 45, OA occurs more frequently in men; although after age 45, OA is more common in women. OA of the hand is particularly common among women.
  • Joint injury or overuse caused by physical labor or sports. Traumatic injury to a joint increases your risk of developing OA in that joint. Joints that are used repeatedly in certain jobs may be more likely to develop OA because of injury or overuse.
  • Obesity. The chances of getting OA generally increase with the amount of weight joints have to bear. In the knee, which is a major weight-bearing joint, being overweight during midlife or the later years is the strongest risk factor for developing OA.
  • Joint alignment. People with joints that move or fit together incorrectly, such as in bowlegs, dislocated hips, or double-jointedness, are more likely to develop OA in those joints.
  • Hereditary gene defect. A defect in one of the genes responsible for a cartilage component called collagen can cause deterioration of cartilage.
  • Certain diseases. Some diseases, such as rheumatoid arthritis, change the normal structure and function of cartilage and may increase your risk of developing OA.

What causes rheumatoid arthritis?

RA is an autoimmune disease. This means the body's natural immune system does not operate as it should; it attacks healthy joint tissue, initiating a process of inflammation and joint damage.

The exact cause of RA is not yet known. Although scientists do know that many factors may contribute to the development of RA. Genetic, or hereditary, factors play a role. Scientists have shown certain genes that play a role in the immune system may be involved in determining whether or not you develop RA. However, some people with RA do not have these particular genes, and other people who do have the genes never develop the disease.

Environmental factors may also contribute to the cause of the disease. Researchers have found that RA can be triggered by an infection, possibly a virus or bacterium, in people who have an inherited tendency for the disease. However, RA is not contagious; you can't "catch it" from anyone.


This quick guide is supported by Pfizer.