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What is it?

Septic arthritis, also called infectious or bacterial arthritis, is not as common as some of the other types of arthritis. However, it needs to be diagnosed and treated quickly because it can destroy joints in a short period of time. In cases where the infection spreads to the blood causing sepsis, it can become a life-threatening condition.

Septic arthritis occurs most often following direct injury to the joint in persons with artificial joints, and in persons with bacteria in the blood (bacteraemia). Additional risk factors include age greater than 80 years, having diabetes or rheumatoid arthritis, and recent surgery or injection into the affected joint. The knee and the hip are the most commonly infected joints.

In most cases of septic arthritis the joint becomes hot, red, swollen, painful and difficult to move, and there is often a fever. More than one joint may be affected. In patients with prosthetic joints symptoms such as loosening of the joint, chronic pain or poor wound healing may be due to septic arthritis.

The acute form of septic arthritis is usually caused by bacteria. Infection with Staphylococcus aureus or streptococci — which are types of bacteria commonly found on skin — is the most common cause. However a wide variety of organisms have been associated with septic arthritis including the bacteria that cause gonorrhoea. The rare chronic form may be due to the organism that causes tuberculosis or the yeast Candida albicans.

What tests are used?

The following are common tests used to diagnose septic arthritis or to monitor it’s treatment:

It is important to identify the organism causing the septic arthritis because this will mean the most effective treatment can be given. Ideally cultures of the blood or joint fluid should be performed before antibiotic are started. Many bacteria struggle to grow in cultures once antibiotics have been given.

What treatments exist?

Treatment is with antibiotics. The exact antibiotic used will depend on the causative bacteria, which can usually be identified from a culture. Then, the antibiotic therapy can be adjusted depending on the results of antibiotic susceptibility tests, which determine what specific antibiotics the bacterium is most sensitive to.

High doses of antibiotics are required to get into the joint space. For this reason, septic arthritis is usually treated with antibiotics given through a vein, often for a number of weeks. Once the initial infection has settled down treatment may be changed to antibiotic tablets.

Drainage of the infected joint fluid is an important part of the treatment. Sometimes this can be accomplished with needle aspiration. Often surgical ‘wash-out’is required to clear the joint of all infection. In severe cases this procedure may need to be repeated several times.

Infections of prosthetic joints are difficult to treat because bacteria stick to a film on the metal surfaces where they cannot easily be killed by antibiotics. People with such infections may need multiple surgical procedures and much longer treatment with antibiotics. Sometimes replacement of the entire joint after a period of antibiotic treatment is required to clear the infection.

Last Review Date: June 13, 2011