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. Septic arthritis occurs most often following direct injury, such as in an accident, in persons with artificial joints, and in persons with bacteria in the blood
(bacteraemia) due to certain infections, such as a skin infection.
Additional risk factors include age (older than 80 years), having
diabetes or
rheumatoid arthritis, and recent joint surgery. The knee and the hip are the most commonly infected joints. The joint becomes hot, red, swollen, painful and difficult to move, and there is often a fever. More than one joint may be affected.
The acute form of septic arthritis is usually caused by bacteria, such as
staphylococcus,
streptococcus pneumoniae, and
group B streptococcus and sometimes by the organisms that cause gonorrhoea and Lyme disease. 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:
- Blood culture;
- Culture of joint fluid or synovial fluid analysis; and
- X-ray of joint(s).
What treatments exist?
Treatment is with antibiotics. The exact antibiotic used will depend on the causative bacteria, which can 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.
In some cases, the build up of synovial fluid in the joint that occurs because of the infection requires aspiration (using a needle and suction to remove the liquid); in more severe cases, surgery may be needed to drain the fluid.
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