Septic arthritis (general)

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Background

  • Most important diagnostic consideration in acute joint pain (can destroy joint in days)
  • Knee most commonly involved in adults; hip most common in pediatric
  • Most often seen in patients >65yr
  • Most common causative organisms

Clinical Features

  • Fever
  • Warm, red, painful, swollen joint
  • Decreased range of motion to active and passive movement
  • Gonococcal arthritis
    • Urethritis/vaginitis may be absent
    • May have prodromal phase:
      • Migratory arthritis and tenosynovitis predominate before pain and swelling occurs
      • Macularpapular rash or pustules especially on hands/feet may proceed overt arthritis
  • Endocarditis should be considered in the presence of 2 or more affected joints

Differential Diagnosis

Monoarticular arthritis

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Algorithm for Monoarticular arthralgia

Evaluation

Work-Up

  • Arthrocentesis with synovial fluid analysis
    • Synovial fluid culture only (not 100% sensitive)
  • CBC
  • ESR
    • Sn 94% (with 15mm/h cut-off)[1]
  • CRP
    • Sn 92% (with 20mg/L cut-off)
  • Blood Culture
  • Gonorrhea culture (urethral/cervical/pharyngeal/rectal)
  • Imaging
    • Helpful for excluding other diagnoses (e.g. trauma, osteo)
  • Immunocompromised
    • Consider mycobacterial or fungal arthritis
    • Leukemia history: predisposed to Aeromonas infections
  • Periprosthetic infection
    • Non-emergent: acute microbiological diagnosis is more important than rapid antibiotics
    • Diagnose with two synovial fluid cultures (avoid collection from a draining sinus)
    • CRP >100mg/L during first 6 weeks post-op warrants aspiration and may be used to differentiate from superficial skin infection

Arthrocentesis of synoval fluid

Synovium Normal Noninflammatory Inflammatory Septic
Clarity Transparent Transparent Cloudy Cloudy
Color Clear Yellow Yellow Yellow
WBC <200 <200-2000 200-50,000

>1,100 (prosthetic joint)

>25,000; LR=2.9

>50,000; LR=7.7

>100,000; LR=28

PMN <25% <25% >50%

>64% (prosthetic joint)

>90%

Culture Neg Neg Neg >50% positive
Lactate <5.6 mmol/L <5.6 mmol/L <5.6 mmol/L >5.6 mmol/L
LDH <250 <250 <250 >250
Crystals None None Multiple or none None

Management

Arthrocentesis

  • Treatment based on diagnostic studies

Antibiotics

For adults treatment should be divided into Gonococcal and Non-Gonococcal

Gonococcal

Non-Gonococcal

Pediatrics

Consultation

  • Consult ortho for joint irrigation in OR if joint aspirate is indicative of infection

Disposition

  • Admit all to ortho

See Also

External Links

References

  1. Hariharan, H, et al. Sensitivity of Erythrocyte Sedimentation Rate and C-reactive Protein for the Exclusion of Septic Arthritis in Emergency Department Patients. J of Emerg Med. 2010; 40(4):428–431. http://dx.doi.org/10.1016/j.jemermed.2010.05.029