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
- Full blood count (FBC)
- Culture of joint fluid or synovial fluid analysis
- X-ray of joint(s)
What treatments exist?
Treatment is with antibiotics. The exact antibiotic used may depend on the bacteria, which can be identified from growing the bacteria in a laboratory. Then, the antibiotics can be adjusted depending on the results of the laboratory antibiotic susceptibility tests, which show what antibiotics have been found to work.
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.