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Septic Arthritis

Study guide:


  • Infections of the joint space: known as septic arthritis, pyogenic arthritis,

    suppurative arthritis, purulent arthritis, or pyarthrosis.

  • “Septic Arthritis” usually refers to bacterial arthritis.


  • More common in childhood > adulthood.

  • More common in children < 3 Y/O.

  • M: F ratio is 2:1.

  • Hip and knee joints are the most commonly involved joints.

Risk Factors:

  • Umbilical vessel catheterization 

  • Central line

  • Joint surgery & prosthetic joints

  • Hemoglobinopathy

  • Immunodeficiency

  • Osteoarthritis

  • Bacteremia from endocarditis

  • Degenerative joint disease

  • Rheumatoid arthritis

  • IV Drug Abuse

Routes for Transmission:

  • Hematogenous spread accounts for most cases of bacterial arthritis.

  • Polymicrobial infections should be considered in patients with direct inoculation.

  • Contiguous extension of infection to the joint space is rare, except when a concurrent osteomyelitis is present.

Prosthetic joint has the greatest risk factor for septic arthritis. 


  • According to the Microbiology:

S. aureus is the most common organism causing septic arthritis in all age groups.
K.Kingae is the most common cause of gramnegative septic arthritis.
S. epiderdimis is the most common organism associated with prosthetic joints.
  • According to age Group:

Clinical Presentation:

  •  The joint is warm, red, & immobile + palpable effusion.

  • Acute onset of fever & chills -> bacteremia.

  •  Irritability & poor feeding -> in neonates

  • Other associated symptoms:


  • Needle aspiration of the joint (arthrocentesis) the best initial
    and most accurate test:

    • High WBCs predominantly neutrophils.

    • Gram staining.

    • Culture.

  • Others:

    • CBC: ^ WBCs.

    • ESR and C-reactive protein.

    • Blood culture.

    • Ultrasound -> joint effusion.


  • General:

    • Septic shock -> fluid resuscitation.

    • Pain and fever -> NSAIDs.

    • Physical therapy.

  • The cornerstone therapy is:

  1. Antibiotics:

    • Specific therapy:

    • Ceftriaxone and Vancomycin are the best initial empirical therapy. (before culture)

    • Empirical therapy

Ceftriaxone and Vancomycin are the best initial empirical therapy. 

2.  Surgical management:

  1. Arthrotomy esp. for hip septic arthritis.

  2. Arthroscopy esp. for knee septic arthritis.

  3. Needle Aspiration any joint except for hip septic arthritis.


  • Joint laxity, subluxation, or dislocation.

  • Joint restriction and contracture.

  • Limb-length discrepancy (if the growth plate is involved).

  • Avascular necrosis of the femoral head.

  •  Enlargement of the femoral head (Coxa Magna Deformity).

  • Pathologic fractures.

Rx of infected prosthetic joints:

The first stage is to remove the joint, treat with antibiotics for 6 to 8 weeks, & then replace the joint.

Even with appropriate management, approximately 40% of patients with hip involvement and 10% of patients with knee involvement develop significant complications! 


  1., (2015). Bacterial arthritis: Clinical features and diagnosis in infants and children. [online] Available at: arthritis-clinical-features-and-diagnosis-in-infants-and-children [Accessed 8 Dec. 2015].

  2., (2015). Bacterial arthritis: Treatment and outcome in infants and children. [online] Available at: [Accessed 8 Dec. 2015].

  3., (2015). Bacterial arthritis: Epidemiology, pathogenesis, and microbiology in infants and children. [online] Available at: microbiology-in-infants-and-children [Accessed 8 Dec. 2015].

  4., (2015). Pediatric Septic Arthritis: Background, Etiology, Epidemiology. [online] Available at: [Accessed 8 Dec. 2015].

  5. Kliegman, R. (n.d.). Nelson textbook of pediatrics.

  6. Fischer, C. (n.d.). Master the boards.

  7., (2015). Case Based Pediatrics Chapter. [online] Available at: [Accessed 9 Dec. 2015].

  8. Fischer, C. (n.d.). Master the boards.

  9. Le, T., Bhushan, V. and Singh Bagga, H. (2010). First aid for the USMLE step 2 CK. New York: McGraw-Hill


Written by: Roaa Amer.

Reviewed by: Lama Al Luhidan

Format editor: Roaa Amer and Haifa Al Issa

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