Health

Infectious arthritis, as indicated by its name, is caused by an infection with bacteria, viruses, or fungi. Infections usually spread to the joints from the site of origin by way of the bloodstream, so it may be difficult to determine where the infection started. Once the infection reaches the joint, it can cause warmth, pain, and swelling, sometimes accompanied by fever and chills. Occasionally, infection is introduced directly, as with a puncture wound or major injury.

Infectious arthritis due to bacteria most often affects the knee, although infections that are caused by viruses are most likely to affect small joints like fingers or toes. People with other joint diseases, such as rheumatoid arthritis, are slightly more likely to develop infectious arthritis, although the overall frequency of infectious arthritis, even among people with existing joint problems, is relatively low.

Causes of infectious arthritis

Viruses are the most common cause of infectious arthritis, but bacterial infections tend to be the most serious.

Viral infections. Many viruses may trigger arthritis, including the viruses that cause colds and other respiratory infections, as well as more serious illnesses such as AIDS and hepatitis. Multiple joints can be affected at the same time, and the symptoms sometimes appear similar to those of rheumatoid arthritis. Treating the virus usually alleviates arthritic symptoms, although chronic conditions such as HIV infection and some forms of viral hepatitis can cause ongoing joint pain.

Bacterial infections. Lyme disease, which is caused by the bacterium Borrelia burgdorferi, is transmitted primarily through bites of deer ticks. An infected person may develop a large, round rash with a central, clear area known as a "bull's-eye," as well as fatigue and other flulike symptoms. But the symptoms may be subtle or mistaken for something else, so Lyme disease may not be diagnosed promptly. If Lyme disease goes untreated and advances, arthritis may develop. This type of arthritis usually affects one or both knees but can also affect other larger joints.

Arthritic joint pain also affects about a third of people with gonorrhea, a sexually transmitted bacterial infection. Staphylococcus bacteria, which can cause infections through cuts or breaks in the skin and through contaminated food, can be released in the bloodstream and spread to the knees and other joints, causing intense pain and swelling. If a staph infection is not treated promptly, it can cause serious joint damage within just a few days. Tuberculosis, a bacterial infection that usually affects the lungs, can cause arthritis in the spine and in other large joints, such as the knees or hips. Reactive arthritis and Reiter's syndrome are caused by infection with bacteria in the genitourinary or digestive tracts.

Diagnosing infectious arthritis

To help determine the infectious agent, your doctor may withdraw a small amount of fluid from the affected joint and have it analyzed. The doctor may also order blood and urine tests. While these tests are unable to pinpoint every infectious agent, blood tests that measure antibodies against some of the more chronic viral diseases, such as hepatitis B, hepatitis C, and HIV, are often helpful.

If you are a woman and a sexually transmitted disease is suspected, the doctor may perform a pelvic exam. If you are a man, your doctor may swab your penis and test your urine.

Treating infectious arthritis

Any infections should be treated as soon as possible in order to prevent permanent damage. If joint pain and complications have developed, these will be treated separately. You may need to briefly immobilize your affected joint while recovering from the infection. But it's best to become active again as soon as you are able, because exercise and physical therapy can help you regain your strength and mobility.

Treating viral infections. Viral infections do not carry the same risk of joint damage as bacterial infections do, but the infection itself may be harder to treat, as viruses do not respond to antibiotics. Some viral infections, such as HIV or hepatitis C infection, can be treated with antiviral therapy. For other types of viral infections, taking aspirin or ibuprofen can help reduce pain and swelling while the infection runs its course.

Treating bacterial infections. If you have a bacterial infection, your doctor will probably start with an antibiotic. If the infection is advanced or if joint damage has already occurred, the doctor may recommend that you be hospitalized so that your affected joint can be drained (which may require minor surgery) and given adequate rest, and so that you can receive antibiotics intravenously. If your joint is seriously damaged, you may need surgery in order to remove damaged tissue and reconstruct the joint.

Preventing infectious arthritis

It's much better for your health if you can prevent infectious arthritis from developing at all. That means trying to avoid infections, especially those that can cause permanent joint damage. You can reduce exposure to viruses by washing your hands frequently, especially during cold and flu seasons. You can protect yourself from sexually transmitted bacteria and viruses by practicing safe sex. Promptly cleaning wounds and cooking food thoroughly will reduce your exposure to staph infections. To avoid Lyme disease, use tick repellant when walking in the woods or tall grass, wear long-sleeved shirts, and tuck long pants into socks.

Source: from Harvard Health Publications, Copyright © 2008 Harvard University. All rights reserved. Harvard Medical School does not endorse products.
Used with permission of StayWell.
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