Septic arthritis

Septic arthritis develops when bacteria or other tiny disease-causing organisms (microorganisms) spread through the blood to a joint. It may also occur when the joint is directly infected with a microorganism from an injury or during surgery. Joints that are commonly affected are the knee and hip.

Most cases of acute septic arthritis are caused by staphylococcus or streptococcus bacteria.

Chronic septic arthritis (which is less common) is caused by organisms including Mycobacterium tuberculosis and Candida albicans.

The following conditions increase your risk for septic arthritis:

• Artificial joint implants
• Bacterial infection somewhere else in your body
• Presence of bacteria in your blood
• Chronic illness or disease (such as diabetes, rheumatoid arthritis, and sickle cell disease)
• Intravenous (IV) or injection drug use
• Medicines that suppress your immune system
• Recent joint injury
• Recent joint arthroscopy or other joint surgery

Septic arthritis may be seen at any age. In children, it occurs most often in those younger than 3 years. The hip is often the site of infection in infants. Most cases are caused by the bacteria group B streptococcus. Another common cause is Haemophilus influenza, especially if the child has not been vaccinated for this bacterium.

Symptoms usually come on quickly. There is a fever and joint swelling that is usually in just one joint. There is also intense joint pain, which gets worse with movement.

Symptoms in newborns or infants:

• Crying when infected joint is moved (for example, during diaper changes)
• Fever
• Not able to move the limb with the infected joint (pseudoparalysis)
• Fussiness

Symptoms in children and adults:

• Not able to move the limb with the infected joint (pseudoparalysis)
• Severe joint pain
• Joint swelling
• Joint redness
• Fever

Chills may occur, but are uncommon.

Your health care provider will examine the joint and ask about the symptoms.

Tests that may be done include:

• Aspiration of joint fluid for cell count, examination of crystals under the microscope, Gram stain, and culture
• Blood culture
• X-ray of affected joint
• Blood work including complete blood count (CBC)

Antibiotics are used to treat the infection.

Resting, raising the joint above heart level, and using cool compresses may help relieve pain. After the joint starts to heal, exercising it can help speed up recovery.

If joint (synovial) fluid builds up quickly due to the infection, a needle may be inserted into the joint to withdraw (aspirate) the fluid. Severe cases may need surgery to drain the infected joint fluid and irrigate (wash) the joint.

Recovery is good with prompt antibiotic treatment. If treatment is delayed, permanent joint damage may result.

Contact for an appointment with your provider if you develop symptoms of septic arthritis.

Preventive (prophylactic) antibiotics may be helpful for people at high risk.

Bacterial arthritis; Non-gonococcal bacterial arthritis

Cook PP, Siraj DS. Bacterial arthritis. In: Firestein GS, Budd RC, Gabriel SE, Koretzky GA, McInnes IB, O'Dell JR, eds. Firestein & Kelley's Textbook of Rheumatology. 11th ed. Philadelphia, PA: Elsevier; 2021:chap 116.

Robinette E, Shah SS. Septic arthritis. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 705.

Updated by: Jatin M. Vyas, MD, PhD, Associate Professor in Medicine, Harvard Medical School; Associate in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.