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Updated: Dec 22 2021

Septic Arthritis

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  • Snapshot
    • A 52-year-old man presents to his emergency department for worsening knee pain. He reports that his symptoms began approximately 10 days ago and is unable to bear weight on the affected knee. Medical history is significant for poorly controlled type II diabetes mellitus. On physical exam, the right knee is erythematous, swollen, and tender to palpation. There is decreased range of motion on the affected joint. Laboratory testing demonstrates an elevated erythrocyte sedimentation rate and C-reactive protein. An athrocentesis is obtained and demonstrates a white blood cell count of 65,000 cells/μL and gram-positive organisms.
  • Introduction
    • Clinical definition
      • infection of a joint leading to arthritis that can be caused by
        • bacteria
        • fungi
        • mycobacteria
  • Epidemiology
    • Risk factors
      • increasing age
      • diabetes mellitus
      • rheumatoid arthritis
      • prosthetic joints
      • intravenous drug abuse
      • skin infection
      • alcohol use
      • sexual activity
  • Etiology
    • Staphylococcus aureus
      • most common cause
    • Streptococci
      • second most common cause of nongonococcal arthritis
    • Neisseria gonorrhoeae
      • suspect in healthy and sexually active patient
    • Pseudomonas aeruginosa
      • typically seen in healthcare-associated infections
    • Borrelia burgdorferi
      • typically seen in patients in endemic areas
    • Mycobacterium tuberculosis
    • Staphylococcus epidermidis
      • typically seen in prosthetic joint infections
    • Pathogenesis
      • infectious agent can be spread to the joint by
        • hematogenously
        • direct inoculation
        • contiguously from the adjacent skin (e.g., cellulitis and cutaneous ulcers)
      • once the infectious agent arrives to the synovial membrane an inflammatory response ensues
  • Presentation
    • Symptoms
      • fevers may be present
      • joint pain
    • Physical exam
      • in most cases 1 joint is affected
        • a joint that is
          • warm
          • erythematous
          • swollen
          • restricted to movement
  • Imaging
    • Radiography
      • indication
        • can be used to get a baseline assessment of joint damage
  • Studies
    • Labs
      • ↑ erythrocyte sedimentation rate and C-reactive protein
    • Arthrocentesis
      • the best initial test for the evaluation for septic arthritis
    • Synovial fluid culture
      • the most accurate test and must be performed before antibiotic administration
      • findings
        • fluid is usually purulent
        • Gram stain may be positive
          • 30-50% sensitive
        • white blood cell count > 50,000 cells/μL
  • Differential
    • Gout
    • Pseudogout
    • Inflammatory arthritis (e.g., rheumatoid arthritis)
    • Viral arthritis (e.g., hepatitis B and C and parvovirus B19)
  • Treatment
    • Medical
      • intravenous empiric antibiotics
        • indication
          • treatment of choice after athrocentesis is performed to target the most likely organism
            • best if a minimum of 2 blood cultures are performed prior to administering antibiotics
            • antibiotics then becomes tailored to the specific organism when susceptibility results return
        • drugs
          • vancomycin + a third-generation cephalosporin
            • an initial empiric treatment option for septic arthritis
          • vancomycin
            • used when
              • Gram stain of synovial fluid shows gram-positive cocci
          • third-generation cephalosporin
            • used when
              • Gram stain of synovial fluid shows gram-negative bacilli
    • Operative
      • joint drainage
        • indication
          • used along with antibiotics to treat septic arthritis
            • septic arthritis represents a closed abscess
        • modalities
          • needle aspiration
          • arthroscopic drainage
          • arthrotomy
  • Complications
    • Osteomyelitis
    • Sepsis
  • Prognosis
    • Dependent on a number of comorbid conditions (e.g., age and immunosuppresion)
      • ranges 10-15%
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