Septic arthritis

septic arthritis

Septic arthritis

Description, Causes and Risk Factors:

Alternative Name: Infectious or bacterial arthritis.

Abbreviation: SA.

Septic arthritis is a form of arthritis where a joint gets infected by either bacteria, viruses, fungi, or parasites causing symptoms of arthritis. Typically, septic arthritis affects a single large joint, such as the knee or hip arthritis, but it is possible for several joints to be infected as well. People with artificial joints are at the highest risk to get septic arthritis, but it can happen to people with natural joints as well.

The cause of septic arthritis is a bacterial infection within a joint or joints. These bacteria cause inflammation within the joint that can ultimately lead to damage to the cartilage, underlying bone, and joint capsule.

    In infants under one year of age, the most common septic arthritis cause is Staphylococcus aureus (A bacterium that causes illnesses ranging from minor skin infections and abscesses, to life-threatening diseases such as pneumonia, meningitis and septicemia) or Group B Strep. Haemophilus influenzae are the most common causes in children under five years of age.

  • For adults, the most common cause of septic arthritis is an infection with Neisseria gonorrhoeae.

  • Mycobacterium tuberculosis, which causes tuberculosis (TB), can also cause septic arthritis. Infection with the bacteria that causes Lyme disease (Borrelia burgdorferi) may also lead to septic arthritis.

Other bacteria may include:

    S. aureus, 61%.

  • MRSA, 50%.

  • ?-hemolytic strep, 15%.

  • Gram negative, 17%.

  • S. pneumoniae, 3%.

  • Polymicrobial, 4%.

Risk Factors May Include:

    Infants and young children are at greatest risk for the condition.

  • Osteomyelitis (an inflammation of bone and bone marrow).

  • Previous joint damage

  • Chronic arthritis.

  • Rheumatoid arthritis, gout, or osteoarthritis.

  • Alcoholism or IV drug abuse.

  • Immunosuppressive medicines.

  • Having recently undergone certain procedures, such as knee replacement, hip replacement, or knee arthroscopy.

  • Some studies have indicated that women and homosexual men are more prone to developing septic arthritis however the reasons why have not yet been determined.


Symptoms may include:


  • Chills.

  • Irritability.

  • Severe joint pain.

  • Swelling of the affected joint.

  • Heat around the affected joint.

  • Fatigue and malaise.

  • Nausea and vomiting.

  • Painful range of motion (ROM).

  • This disease can even send the victim into septic shock causing damage to bones, cartilage and to the heart.


Differential diagnosis May Include:

    Gout and Pseudogout.

  • Bursitis.

  • Rheumatoid arthritis (RA), usually symmetrical polyarthritis.

  • Viral arthritis

  • Small joints symmetric polyarthritis

  • Reactive arthritis.

  • Rheumatic fever.

  • Oligoarthritis.

Diagnosis of disease is largely clinical, guided by investigations and the opinion of skilled clinicians.The following are common tests used to diagnose septic arthritis:

    Blood culture.

  • Culture of joint fluid or synovial fluid analysis.

  • X-ray of joints.

  • ESR/CRP.

  • UA and culture.


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.

Antibiotic therapy:

    If gram positive cocci and community acquired, the drug of choice is cefazolin 1-2 gm IV Q8. If non-community acquired, vancomycin is the drug of choice 30mg/kg IV Qd in two divided doses.

  • If gram negative, ceftazidime 2 gm IV Q8 or, ceftriaxone 1 gm Q24. Add on gentamicin if the patient is an intravenous drug user (IDU) for pseudomonas coverage. Ceftriaxone if the drug of choice for suspected gonococcal septic arthritis. Modify with susceptibilities. Duration is usually 2 weeks of parenteral antibiotics and usually 14-21 days of oral therapy. Shoulder may require longer therapy 2-6 weeks.

Rest, immobilization, elevation, and warm compresses may help relieve pain. Performing exercises for the affected joint aids the recovery process.

If synovial fluid builds up rapidly in the joint as a result of the infection, frequent aspiration of the fluid by inserting a needle into the joint or surgery may be needed. Severe cases may need surgery to drain the infected joint fluid

Joint drainage:

    Options are closed needle aspiration or arthroscopic drainage.

  • Serial taps may be necessary on a daily basis and should be continued until cultures are clear and synovial WBC (white blood cell) decreases. Controversies exist as to whether patients need operative drainage vs needle aspirations. A few studies have shown that open surgical drainage may suggest higher morbidity and mortality, although most of these were retrospective studies.

  • Arthroscopy is preferred for the hip, shoulder, and knee.

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.


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