When we think of invading bacteria, we usually don't think of our joints as a potential target. But if there's an infection somewhere in your body, the germs can travel through your bloodstream to attack a joint. Bacteria can also enter a joint directly, either right after surgery or from an injury, for example. Either way, the infected joint becomes swollen, inflamed, and painful. Doctors call this condition septic arthritis, bacterial arthritis, or infectious arthritis.
Germs don't have to invade a joint to cause arthritis. Some types of infections can trigger an unusual reaction in the body that results in widespread inflammation, pain, and swelling in the joints. This is called reactive arthritis. Reactive arthritis can result from a bout of salmonella, shigella, and campylobacter contracted through food poisoning. A case of reactive arthritis can also follow certain sexually transmitted infections, including chlamydia, gonorrhea, and HIV.
Both septic arthritis and reactive arthritis can cause pain and swelling in a joint. Septic arthritis most often occurs in one joint, usually a knee, shoulder, or wrist, but it can involve several. It typically causes a mild fever, and the patient may feel like it's impossible to move the joint.
In the case of reactive arthritis, symptoms usually arise in several joints at once, most often the knee, ankle, and toes. Frequently, one or more toes swell into the shape of a sausage. (Naturally enough, this condition is called "sausage toe.") Some people with reactive arthritis also have inflammation in the eyes, a burning sensation during urination, pain in the Achilles tendon, fever, and weight loss.
Who's at risk
Septic arthritis is more common in the very young, the very old, and anyone with a weakened immune system, including injection drug users and patients with cancer, diabetes, or HIV. People who have recently had joint surgery are also at risk.
Reactive arthritis is most common among men in their 20s or 30s. (When a young man has several inflamed joints, reactive arthritis is a possible cause.) Genes also play an important role in the disease. According to the National Institute of Arthritis and Musculoskeletal Diseases, about 80 percent of patients with reactive arthritis have a particular gene called HLA-B27.
Septic arthritis is generally the easiest to spot. A doctor then collects fluid from the joint to confirm an infection and, hopefully, identify the bacteria involved. Blood tests and x-rays can help give a complete picture of the situation.
Reactive arthritis is a little less clear-cut. Doctors usually diagnose the condition based on the collection of symptoms. A doctor may run tests to check for any hidden sexually transmitted diseases, and blood tests can determine whether a person carries the HLA-B27 gene.
Medications attack septic arthritis at the source. Antibiotics usually clear up the problem within three to six weeks; physicians may also drain the area of infection. Antibiotics are especially effective when doctors can identify the type of bacteria involved.
Antibiotics can also help patients recover from reactive arthritis, but only if they have an active bacterial infection. If the infection has already come and gone, antibiotics won't do much good.
Most patients with reactive arthritis are treated with nonsteroidal anti-inflammatory drugs, like indomethacin (Indocin) or ibuprofen (Motrin). These drugs ease inflammation and greatly reduce symptoms. Arthritis in the knee is sometimes treated with injections of corticosteroids, another type of anti-inflammatory drug.
If the disease persists, a doctor may prescribe drugs that slow down the immune system. A doctor may also recommend exercises to keep the joint strong and flexible.)
The long-term outlook
With prompt treatment, most people with septic arthritis recover completely. If treatment is delayed, however, joints may become permanently damaged. Likewise, most people with reactive arthritis get better with treatment. As with any serious illness, patients who take their medicine as directed and follow their doctors' advice have the best chance of recovery.
Infectious arthritis. Mayo Clinic online..
National Institute of Arthritis and Musculoskeletal Diseases. Questions and Answers About Reactive Arthritis.
American Academy of Family Physicians. Reactive arthritis: What you should know.
National Institutes of Health. Medline Plus. Non-gonococcal (septic) bacterial arthritis. November 2001.
Werner FB and K Segal. Reactive arthritis (Reiter's syndrome). American Family Physician. Vol. 60(2): 499-503.