Septic Arthritis in Children

Written by

Dr Emily Kong
MBBS | Accredited Orthopaedic Registrar

Weekly Presentation 26th March 2010

  • Septic arthritis must be ruled out in the child with a painful joint
  • Delay in treatment or failure to diagnose problematic
  • Difficult patient group to obtain history and examination
  • Prognosis significantly improved:
    • Mortality reduced from 50% in 1874 to <1% in 1974

Incidence

  • USA: 1 in 100,000 unchanged over a decade
  • Israel: 37 in 100,000
  • Malawi: 1 in 5000
  • Africa: 1 in 20,000

Causative Organisms

  • Most common: Staph aureus
  • Group A Strep, Enterobacter
  • H. influenza
    • significantly decreased by vaccination
  • Salmonella
    • common in children with sickle-cell disease
  • Kingella kingae
    • unusual
  • Beware emergence of MRSA

Risk Factors

  • Young age
  • Male gender
  • Increased susceptibility to infection
  • Umbilical artery catheterization

Clinical Symptoms and Signs

  • Painful, swollen joint
  • Effusion
  • Restricted ROM
  • Tenderness
  • Increased warmth
  • Systemically unwell, irritability, fever
  • Cellulitis or abscess formation
  • Limited spontaneous movement of affected joint

Investigations

Septic Arthritis, radiograph of the left hip in septic arthritis caused by melioidosis
Radiograph of the left hip in septic arthritis caused by melioidosis. Image by N. P. Weerasinghe, H. M. M. Herath and T. M. U. Liyanage, Wikimedia Commons, CC BY 4.0.

Laboratory

  • WCC
    • Usually elevated in older children,
    • sometimes elevated in younger children,
    • rarely elevated in neonates
  • ESR
    • alone sensitivity 79%
    • with elevated temp, elevated WCC and NWB – 98%
  • CRP
    • highest predictive value for septic arthritis

Imaging

  • Plain XR
    • Differential Diagnosis
      • osteomyelitis,
      • fracture,
      • neoplasia,
    • increased joint space may indicate effusion
  • Ultrasound
    • most sensitive tool for detection of hip effusion,
    • false negative rate 5%,
    • guided aspiration
      • can evacuate pus,
      • decrease damage to articular surfaces,
    • DDx other arthritides
    • direct ABx Rx,
    • caution with –ve US with symptoms <24hrs or bilateral disease
  • MRI
    • sensitive and specific, can differentiate from osteomyelitis and non-infective causes of hip pain,
    • signal intensity alterations and contrast enhancement of bone marrow and adjacent soft tissue
  • Bone scan
    • lacks sensitivity and specificity

Treatment

Management Algorithms

  • Attempt to improve diagnosis and treatment
  • Not applicable in all settings
  • Should supplement, not substitute, clinical decision-making

Antibiotics

  • Wide support for early administration and not withheld before diagnosisif clinical suspicion
  • Choice based on most likely organism
  • Initially administer i/v, then oral when clinical improvement evident
  • Debate on duration of i/v: 2-7wks
  • Growing evidence for short-course i/v therapy – 7 days

Joint Aspiration Vs Arthrotomy + Washout

  • Arthrotomy best method of Rx
  • Doubt with adequacy of decompression achieved with U/S guided aspiration
  • Repeat aspirations may be required
  • Only significant difference in open Vs arthroscopic hip washout was shortened inpatient stay

Take-home Message

  • Indicators of poor prognosis:
    • Young age:
      • difficult to Dx, transphyseal vessels in neonates
    • Delay in initiating Rx:
      • if diagnosis delayed by >4 days
        • Excellent outcome in only 15%
    • Organism
      • Staph aureus highly virulent
    • Site
      • worst outcome in hip

Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.