Q. I saw my doctor for pain and inflammation in my knee. He said I have arthritis caused by a bacterial infection. Could this be true?
A. I'll bet that, like many of my patients, you think of arthritis as something caused by wear and tear on a joint. That is the main cause of the most common type of arthritis, osteoarthritis. However, there are other kinds of arthritis, too.
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In rheumatoid arthritis and juvenile idiopathic arthritis, an overactive immune system causes joint inflammation. The causes of rheumatoid arthritis are unknown.
But joints also can become infected with bacteria and fungi. These microbes may directly infect the joint, for example, through a puncture wound or major injury. But more often, the infection spreads to a joint by traveling through the bloodstream from somewhere else in the body. Once the microbe reaches the joint, it can multiply. The immune system recognizes the invading foreigner and tries to wipe it out. The infection and the immune response cause warmth, pain, stiffness and swelling.
Several types of bacteria can cause arthritis. Borrelia burgdorferi, for example, is the bacterium that causes Lyme disease. If Lyme disease goes untreated and advances, arthritis may develop, usually in one or both knees.
Arthritic joint pain also affects some people with gonorrhea, a sexually transmitted bacterial infection. Staphylococcus bacteria is another culprit. If a staph infection is not treated promptly, it can cause serious joint damage within days. Tuberculosis, a bacterial infection that usually affects the lungs, can cause arthritis in the spine and other large joints.
The diagnosis of infectious arthritis is made by removing fluid from the joint through a needle. The microbe causing the infection can usually be identified in that fluid.
Once diagnosed, you'll immediately begin antibiotic treatment. This should eliminate the infection and help prevent permanent joint damage if begun early enough. If your infection is advanced, or if joint damage has already occurred, you may need to be hospitalized.
At the hospital, your affected joint can be drained. Sometimes fluid is repeatedly removed with a needle and syringe. In other cases, a surgeon needs to open the joint and place a drain in it to let the joint fluid constantly leak out of the body. You can also receive antibiotics intravenously if necessary. If your joint is seriously damaged, you may need surgery to remove damaged tissue and reconstruct the joint.
Often you 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. Exercise and physical therapy can help you regain your strength and mobility.
It's much better if you can prevent infectious arthritis from developing in the first place. That means taking steps to avoid infections that can cause infectious arthritis:
• Practice safe sex.
• Promptly clean wounds.
• To avoid Lyme disease, use tick repellent when walking in the woods and tuck long pants into socks.
• Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com.