Septic arthritis

Last Review Date: May 26, 2023

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. It can become a life-threatening condition in cases where the infection spreads to the blood causing sepsis. Most commonly septic arthritis occurs following direct injury to the joint in persons with artificial joints, or may occur in persons with bacteria in the blood (bacteraemia). Additional risk factors include age greater than 80 years or less than 3 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. It is most commonly caused by bacteria that are found on the skin, such as Staphylococcus aureus or streptococci. However a wide variety of organisms have been associated with septic arthritis including the bacteria that cause gonorrhoea. Rarely, a chronic form may be due to other organism such as those that cause 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 enable the most effective treatment to be given. Ideally cultures of the blood or joint fluid should be performed before antibiotics are started. Many bacteria struggle to grow in cultures once antibiotics have been given.

What treatments exist?

The mainstay of treatment is with antibiotics but may also involve surgery.

The antibiotic used will depend on the causative bacteria, identified from a culture of the joint fluid or tissue. The antibiotic therapy may be adjusted as further results of antibiotic susceptibility tests become available and more targeted therapy is possible. As high doses of antibiotics are required to get into the joint space, septic arthritis is usually treated with antibiotics given through a vein (intravenous antibiotics) for a number of weeks. Once the initial infection has settled down treatment may be changed to oral 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 become part of a film (biofilm) 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.

Related pages

On this site
Tests: Blood culture, synovial fluid analysis, C-reactive protein
Conditions: Arthritis

Elsewhere on the web
Web MD Septic arthritis
Medline Plus Infectious arthritis
Kid’s Health Septic arthritis


Baker, DG and Schumacher, HR. Jr. Acute monoarthritis. N Engl J Med 1993;329:1013-1020.

DelPozo, JL and Patel, R. Infection Associated with Prosthetic Joints. N Engl J Med 2009; 361:787-794.

References from Lab Tests Online-US

Primary sources of information for Septic arthritis