Definition

Septic arthritis is inflammation of a joint due to a bacterial or fungal infection. Septic arthritis that is due to the bacteria that cause gonorrhea has different symptoms.

Alternative Names

Bacterial arthritis; Non-gonococcal bacterial arthritis

Causes, incidence, and risk factors

Septic arthritis develops when bacteria or other tiny disease-causing organisms (microorganisms) spread through the bloodstream to a joint. It may also occur when the joint is directly infected with a microorganism from an injury or during surgery. The most common sites for this type of infection are the knee and hip.

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

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

The following conditions increase your risk for septic arthritis:

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

Septic arthritis is uncommon from age 3 to adolescence. Children with septic arthritis are more likely than adults to be infected with Group B streptococcus or Haemophilus influenza, if they have not been vaccinated.

Symptoms

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:

  • Cries when infected joint is moved (example: diaper change causes crying if hip joint is infected)
  • Fever
  • Inability to move the limb with the infected joint (pseudoparalysis)
  • Irritability

Symptoms in children and adults:

  • Inability to move the limb with the infected joint (pseudoparalysis)
  • Intense joint pain
  • Joint swelling
  • Joint redness
  • Low fever

Chills may occur, but are uncommon.

Signs and tests

  • Aspiration of joint fluid for cell count, examination of crystals under the microscope, gram stain, and culture
  • Blood culture
  • X-ray of affected joint

Treatment

Antibiotics are used to treat the infection.

Resting, keeping the joint still, raising the joint, and using cool compresses may help relieve pain. Exercising the affected joint helps the recovery process.

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

Expectations (prognosis)

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

Complications

Calling your health care provider

Call for an appointment with your health care provider if you develop symptoms of septic arthritis.

Prevention

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

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