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
- Toxic synovitis
- Abscess
- Cellulitis
- Primary rheumatologic disorder (i.e. vasculitis)
- Iatrogenic
- Reactive arthritis (post-infectious)
Work-Up
- Arthrocentesis with synovial fluid analysis
- Synovial fluid culture only (not 100% sensitive)
- CBC
- ESR
- Sn 96% (with 30mm/h 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
Treatment
- Joint drainage
- Abx
- Gram stain can be used to guide treatment
- Gram+: vancomycin IV
- Gram- OR gonococcus suspected: Ceftriaxone IV 2gm daily
- Gram stain can be used to guide treatment
- 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)
- Knee Diagnoses
Source
- Tintinalli