Septic arthritis, also called infectious or bacterial arthritis, is an infection in a joint. It 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.It may also become life threatening if the infection spills over into the blood stream causing septicaemia. Thankfully this is an uncommon occurrence due to the widespread use of antibiotics.
Septic arthritis occurs most often from a bacterial infection travelling in your blood stream (bacteraemia). This may be from an infection elsewhere in the body that has now spread, however bacteria can also enter the bloodstream directly via the nose and the gut. It may also occur following direct injury, such as in an accident, especially where there is a cut or a wound that allows germs to enter the joint directly. It can also occur from surgery or a joint injection to a particular joint although this is uncommon. Additional risk factors include age (older than 80 years), being an intravenous drug user, having diabetes or rheumatoid arthritis, having an artificial joint and recent joint surgery. If your immune system is low from conditions such as AIDS or from medications such as chemotherapy you are also more at risk.
Septic arthritis can affect any joint however 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 especially if the cause is bacteraemia where the germs can spread from one area to another. The symptoms usually develop quickly over hours to a few days.
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. In the latter cases the symptoms may develop more slowly.