Arthritis, Septic

Basics

Description

  • Septic arthritis (SA) refers to an infection within a joint
  • The knee is involved in over 50% of cases
  • Bacteria can be introduced into a joint by:
    • Hematogenous spread (most common)
    • Contiguous infection (eg, osteomyelitis, cellulitis)
    • Direct inoculation (bite wounds, trauma, invasive procedures, etc.)
  • Irreversible loss of function in up to 50%
  • Mortality rate reportedly 10–15%

Pediatric Considerations

  • Hip infections are most common:
    • Often in patients with otitis media, upper respiratory tract infections, or history of femoral venipuncture
    • Complications of 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

Etiology

  • 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, preexisting joint diseases, trauma, or prosthesis
    • Skin and soft tissue infections, cutaneous ulcers
    • Indwelling catheters
  • Most common organisms:
    • Staphylococcus aureus: Most common cause of SA among all age groups
    • Methicillin-resistant S. aureus (MRSA): culprit for 1/3 of SA caused by S. aureus
  • Other pathogens:
    • Streptococcal species: Infants and children (particularly Streptococcus agalactiae and Streptococcus pyogenes, respectively) and adults with splenic dysfunction
    • Neisseria gonorrhoeae (GC): Young, healthy, sexually active adolescents and adults as well as an important etiology for newborns
    • Neisseria meningitidis: Typically noted early in the disseminated disease course but can also be appreciated without other signs of meningococcal disease
    • Pseudomonas species: Seen in immunocompromised patients or IVDU
    • Salmonella species: Associated with sickle cell disease/related hemoglobinopathies and children with gastrointestinal symptoms
    • Haemophilus influenzae: Seen in unvaccinated children
    • Mycobacterial species: Immunocompromised hosts or travel to endemic areas
    • Fungal etiologies (Candida species, Sporothrix species, Cryptococcus blastomycosis, Coccidioides species): Immunocompromised patients

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