Septic Arthritis
Septic arthritis is a medical emergency. Bacterial invasion of a joint causes rapid cartilage destruction (chondrolysis) within hours/days due to proteolytic enzymes from WBCs.
1. Etiology
- Most Common: Staph. aureus.
- Sexually Active Young Adults: Neisseria gonorrhoeae (Gonococcal arthritis).
- Infants: Group B Strep.
2. Diagnosis
Kocher Criteria (Pediatric Hip):
1. Non-weight bearing.
2. Fever > 38.5°C.
3. ESR > 40 mm/hr.
4. WBC > 12,000.
(4/4 = 99% chance of septic arthritis).
1. Non-weight bearing.
2. Fever > 38.5°C.
3. ESR > 40 mm/hr.
4. WBC > 12,000.
(4/4 = 99% chance of septic arthritis).
Gold Standard: Joint Aspiration (Synovial Fluid Analysis).
Septic Fluid: WBC > 50,000, >90% PMNs, Low Glucose.
3. Management
- Emergency: Surgical Washout (Arthroscopic or Open Arthrotomy).
- Antibiotics: IV for 2-6 weeks.
- Gonococcal: Often responds to IV Ceftriaxone without surgery (if detected early).
25 Practice MCQs
Q1. The most common organism causing septic arthritis in adults is:
Answer: A). Unless sexually active demographic.
Q2. Synovial fluid WBC count diagnostic for septic arthritis is typically:
Answer: A). Often >100,000.
Q3. Kocher's Criteria are used to diagnose:
Answer: A). Differentiates from Transient Synovitis.
Q4. Gonococcal arthritis typically presents as:
Answer: A). "Arthritis-Dermatitis syndrome".
Q5. Why is septic arthritis an emergency?
Answer: A). Permanent joint damage occurs in days.
Q6. The most common route of infection is:
Answer: A). Bacteria from blood lodge in synovium.
Q7. Position of comfort in septic hip is:
Answer: A). Maximize joint volume to reduce pressure.
Q8. Which joint is most commonly affected in IV drug users?
Answer: A). Often Pseudomonas or MRSA.
Q9. Definitive treatment for septic knee is:
Answer: A). Pus must be drained mechanically.
Q10. Fungal arthritis is usually:
Answer: A). Candida or Aspergillus.
Q11. Syphilitic arthritis (Clutton's Joints) presents as:
Answer: A). Rare manifestation.
Q12. Lyme Arthritis is caused by:
Answer: A). Late stage Lyme disease.
Q13. Glucose levels in septic synovial fluid are:
Answer: A). Bacteria consume the glucose.
Q14. Reiter's Syndrome (Reactive Arthritis) triad is:
Answer: A). Not septic, but sterile inflammation.
Q15. Post-operative rehab starts:
Answer: A). Motion nourishes the remaining cartilage.
Q16. Girdlestone procedure is a salvage for:
Answer: A). Removes the infection source (head/neck).
Q17. Pott's Puffy Tumor is:
Answer: A). Misnomer (It is infection, not tumor).
Q18. Kingella kingae is a common pathogen in:
Answer: A). Hard to culture.
Q19. Which is a complication of septic hip in infants?
Answer: A). Cartilaginous head dissolves.
Q20. "String Sign" of synovial fluid:
Answer: A). Infection breaks down hyaluronic acid, making fluid watery (drops like water, doesn't string).
Q21. Diagnosis of prosthetic joint infection (PJI) relies on:
Answer: A). Biomarker for infection.
Q22. The most common joint affected in children is:
Answer: A). Hip is notorious in infants.
Q23. Can septic arthritis occur without fever?
Answer: A). Do not rely solely on fever.
Q24. Viral arthritis (e.g., Parvovirus B19) is usually:
Answer: A). Good prognosis.
Q25. Antibiotic beads are used to:
Answer: A). Standard in osteomyelitis/septic arthritis.
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