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 commonest 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 may have prodromal phase:
  • Migratory arthritis and tenosynovitis predominate before pain and swelling occurs

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
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)

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

• Arthrocentesis
• Monoarticular Arthritis
• Septic Arthritis (Hip)
• Septic Arthritis (Peds)

Source

• Tintinalli