Arthritis, Septic



  • Bacteria can be introduced into a joint by:
    • Hematogenous spread (most common)
    • Invasive procedures
    • Contiguous infection (e.g., osteomyelitis, cellulitis)
    • Direct inoculation such as plant thorns or nails
  • Acute inflammatory process results in migration of WBCs into joint
  • Synovial hyperplasia, cartilage damage, and formation of a purulent effusion
  • Irreversible loss of function in up to 50%
  • Mortality rate reported as high as 11%

Pediatric Considerations
  • Hip infections are most common:
    • Often in patients with otitis media, upper respiratory tract infections, or history of femoral venipuncture
    • Complications of septic arthritis (SA) of hip in children: Avascular necrosis, epiphyseal separation, pathologic dislocation, and arthritis
  • 50% occur in children <3 yr old
  • Infants present with irritability, fever, and loss of appetite
  • Older children present with fever, and a limp or refusal to bear weight or use joint


  • Risk factors:
    • Old age, infancy
    • Rheumatoid arthritis and degenerative joint disease
    • Intravenous drug user (IVDU), endocarditis
    • Females (gonococcal [GC] infection)
    • Immunosuppression (AIDS, diabetes, chemotherapy, steroid therapy)
    • Repeated joint injections, pre-existing joint diseases, trauma, or prosthesis
    • Skin infection, cutaneous ulcers
  • No bacterial pathogen is identified in 10–20%
  • Most common organisms:
    • Staphylococcus aureus in adults, hip infections (80%), and patients with rheumatoid arthritis or diabetes
    • Multidrug-resistant S. aureus (MRSA) has been noted in some studies to be the most common organism in community-onset adult SA
    • Neisseria gonorrhoeae most common in young, healthy, sexually active patients (incidence has decreased over the past decades due to a decrease in the incidence of mucosal GC infections)
  • Other pathogens: Group A β-hemolytic and group B, C, and G Streptococci:
    • Gram-negative rods (e.g., Pseudomonas aeruginosa, Escherichia coli) in 10% of cases
    • Neisseria meningitidis (12% of patients with meningococcal meningitis)
  • Common in old age, infancy, immunosuppression, and IVDU (Pseudomonas)
  • Anaerobes: Diabetes, prosthetic joints
  • Mycobacterial and fungal causes: Atypical (e.g., in advanced HIV); more indolent course

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