Arthritis, Septic

BASICS

DESCRIPTION

  • Infection due to bacterial invasion of the joint space
  • Systems affected: musculoskeletal
  • Synonyms: suppurative arthritis; infections arthritis; pyarthrosis; pyogenic arthritis; bacterial arthritis

EPIDEMIOLOGY

Gender differences:

  • Gonococcal: female > male
  • Nongonococcal: male > female

Incidence

  • May occur at any age, bimodal incidence with peaks in childhood and age >55 years
  • 40 to 60 cases per 100,000 population/year overall
  • Disseminated gonococcal infection is 3 cases per 100,000 population/year

Prevalence

  • 27% of patients presenting with monoarticular arthritis have nongonococcal septic arthritis.
  • Given rising prevalence of prosthetic joints, infected hardware is now most common form of septic arthritis (~2–10% of all joint recipients)

ETIOLOGY AND PATHOPHYSIOLOGY

  • Multiple pathogens
  • Nongonococcal: Staphylococcus aureus (most common in adults)
    • MRSA risk increased in elderly, intravenous drug users (IVDU), postsurgical
    • Streptococcus spp. (second most common in adults)
    • Gram-negative rods (GNR): IVDU, trauma, extremes of age, immunosuppressed
  • Neisseria gonorrhoeae (most common in young, sexually active adults)
  • Polymicrobial infections: Pantoea agglomerans, Nocardia asteroides; typically occur after penetrating trauma such as bite wounds or organic foreign body penetration
  • Other: rickettsial (e.g., Lyme), fungal, mycobacterial
  • Risk by specific age:
    • <1 month: Staphylococcus aureus, group B Streptococcus (GBS), GNR
    • 1 month to 4 years of age: Staphylococcus aureus, Streptococcus pneumoniae, Neisseria meningitidis, Kingella Kingae (1)
    • 16 to 40 years of age: N. meningitidis, Staphylococcus aureus
    • >40 years of age: Staphylococcus aureus
  • Patients with native joint infection are at increased risk for infection of prosthesis (of same joint should it require replacement).
  • Specific high-risk groups:
    • Rheumatoid arthritis (RA): Staphylococcus aureus
    • IVDU: Staphylococcus aureus, GNR, opportunistic pathogens
    • Neonates: GBS
    • Immunocompromised: gram-negative bacilli, fungi
    • Trauma patients with open injuries: mixed flora
  • Pathogenesis:
    • Hematogenous spread (most common)
    • Direct inoculation by microorganisms secondary to trauma or iatrogenic (e.g., joint surgery)
    • Adjacent spread (e.g., osteomyelitis)
  • Pathophysiology:
    • Microorganisms initially enter through synovial membrane and spread to the synovial fluid.
    • Resulting inflammatory response releases cytokines and destructive proteases leading to systemic symptoms and joint damage.

RISK FACTORS

  • Age >80 years
  • Low socioeconomic status, alcoholism
  • Cellulitis and skin ulcers
  • Violation of joint capsule
    • Prior orthopedic surgery
    • Intraarticular injection
    • Trauma
  • History of previous joint disease
    • Inflammatory arthritis (RA: 10-fold increased risk)
    • Osteoarthritis
    • Crystal arthritides
  • Systemic illness: diabetes mellitus, liver disease, HIV, malignancy, end-stage renal disease/hemodialysis, immunosuppression, sickle cell anemia
  • Risks for hematogenous spread: IVDU, severe sepsis/systemic infection

GENERAL PREVENTION

  • Prompt treatment of skin and soft tissue infections
  • Control risk factors.
  • Immunizations (Streptococcus pneumoniae, N. meningitidis)

COMMONLY ASSOCIATED CONDITIONS

Preexisting joint conditions, previous joint trauma or surgery, prosthetic joint

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