Makindo Medical Notes

Related Subjects: |Monoarticular arthritis |Polyarticular arthritis |Rheumatoid arthritis |Gout |Pseudogout |Septic Arthritis |Osteomyelitis |Systemic Lupus Erythematosus (SLE) |Enteropathic Spondyloarthritis |Reactive Arthritis

🔥 Septic arthritis is an orthopaedic emergency that can rapidly destroy cartilage and cause systemic sepsis. It usually affects a single joint but can be polyarticular in immunocompromised patients. Most cases are bacterial 🦠, though fungal and mycobacterial infections occur, especially in immunosuppressed patients. Prosthetic joint infections require urgent orthopaedic input 👨‍⚕️🦴.

⚡ Key Facts

• Monoarthritis = septic until proven otherwise 🚨
• Pus in a joint destroys cartilage within hours (proteases from neutrophils 🧪).
• Urgent aspiration + antibiotics + washout are essential.

🦠 Common Organisms

• Staphylococcus aureus (MSSA/MRSA) – most common.
• Streptococci (Groups A & B).
• Neisseria gonorrhoeae – young, sexually active adults.
• Gram negatives (E. coli, Pseudomonas) – elderly/immunocompromised.
• Fungi & TB – immunocompromised, endemic regions.

👶 Kocher’s Criteria (Paediatrics)

• Fever >38.5°C 🌡️
• Non–weight bearing 🚶‍♂️❌
• ESR >40 mm/hr or CRP >20
• WCC >12 × 10⁹/L

Probability of septic arthritis rises from 2% (0 factors) → 93% (4 factors).

🔎 Synovial Fluid Analysis

🧾 Initial Management Summary

• Aspiration 💉 → send for Gram stain, culture, crystals.
• Bloods 🧪 → FBC, ESR/CRP, blood cultures.
• Imaging → X-ray baseline; MRI for deep infection.
• Empirical IV Antibiotics (tailor to local policy):
  • Native joint: IV Flucloxacillin 2 g QDS
  • If MRSA risk: add Vancomycin
  • Immunosuppressed/Gram–negative suspicion: add Gentamicin or Ciprofloxacin
  • Prosthetic joint 💍🦴: involve orthopaedics + consider combination therapy
• Drainage – repeated aspiration, arthroscopic washout, or open surgery (especially for hip).
• Duration – typically 2 wks IV ➝ 4 wks oral (total 6 wks).
• Pain & Mobility – NSAIDs, joint rest → physio once acute phase subsides.

🚨 Red Flags

• Prosthetic joint infection
• Hip involvement (difficult aspiration, rapid destruction)
• Immunocompromised host
• Sepsis or haemodynamic instability

References

• Septic Arthritis: Current Concepts (PMC)
• BMJ Clinical Review