Septic arthritis

Background

  • Most important diagnostic consideration in acute joint pain (can destroy joint in days)
  • Knee most commonly involved in adults; hip most common in peds
  • Most often seen in pts >65yr
  • Gonococcal arthritis is the most common cause in adolescents and young adults

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 esp on hands/feet may proceed overt arthritis

Diagnosis

  • Arthrocentesis for 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

DDx

  1. Toxic synovitis
  2. Abscess
  3. Cellulitis
  4. Primary rheumatologic disorder (i.e. vasculitis)
  5. Iatrogenic
  6. Reactive arthritis (post-infectious)

Work-Up

  1. Arthrocentesis with synovial fluid analysis
    1. Synovial fluid culture only (not 100% sensitive)
  2. CBC
  3. ESR
    1. Sn 96% (with 30mm/h cut-off)
  4. Blood Culture
  5. Gonorrhea culture (urethral/cervical/pharyngeal/rectal)
  6. Imaging
    1. Helpful for excluding other diagnoses (e.g. trauma, osteo)
  7. Immunocompromised
    1. Consider mycobacterial or fungal arthritis

Treatment

  1. Joint drainage
  2. Abx
    1. Gram stain can be used to guide treatment
      1. Gram+: vancomycin IV
      2. Gram- OR gonococcus suspected: Ceftriaxone IV 2gm daily
  3. Consult ortho for joint irrigation in OR if joint aspirate is indicative of infection

Disposition

  • Admit all to ortho

See Also

Source

  • Tintinalli