A 69-year-man presented to GP with complaint of pain and swelling in his right knee

A 69-year-man presented to GP with complaint of pain and swelling in his right knee. On examination, joint appear red and warm causing pain on active and passive movements. Septic arthritis is suspected and arthrocentesis is advised. Following is true about septic arthritis:

  • A. Is usually self-limiting
  • B. Mostly affects single joint
  • C. The joint should not be aspirated as it would Introduce more infection
  • D. Blood cultures are mostly negative
  • E. Leucopenia is common

0 voters

Answer: B

Septic arthritis mostly affects single joint (Mono-articular arthritis)

Study Notes:

What is Septic Arthritis?

Septic arthritis is a bacterial infection that finds its way into the joint space. It is usually a medical emergency and needs prompt antibiotics and surgical intervention. It is the most rapid and destructive joint disease but relatively rare in an undamaged joint.

Septic arthritis is usually caused by bacteria but viral and fungal infection can also cause spetic arthritis

What are the Risk Factors:

  • Immunocompromised host (diabetics, HIV, elderly)
  • Prosthetic implants
  • Surgical Interventions
  • IV drug abusers
  • Damaged joints – RA, OA, gout, trauma,


What is the Mechanism of infection?

  • Hematogenous spread (most common) – either skin or upper Respiratory tract.
  • Direct inoculation or spread from contagious focus (e.g. cellulitis)

What are the causative organisms:

  • Staphylococcus aureus (most common)
  • Streptococcus
  • Gram negative rods
  • Gonococcal (N. Gonorrheae) – sexually active young adults

What are the Clinical Features?

  • Acute onset of mono-articular arthritis with pain, swelling, and warmth
  • Constitutional symptoms: fever, chills, sweats, malaise, myalgia, pai

Common sites:

  • Knee (most common)
  • Hip
  • Wrist, shoulder
  • Ankles

How to Diagnose the septic athritis?

  • Leukocytosis
  • Raised ESR, and CRP – can used to monitor response to treatment
  • Best Initial: if septic arthritis is suspected
    • Arthrocentesis (Joint fluid Aspiration)

How septic arthritis is Treated?

Treatment includes empiric antiboitics and removal of infected fluid from joint cavity.

Empiric antibiotics: Used till culture results

  • Third-generation cephalosporin – IV Ceftriaxone, IV Ceftazidime
  • Ampicillin/sulbactam

After The culture results antibiotics are given according to organism:

  • For staphylococcal and streptococcal:
    • Flucloxacillin is an antibiotic of choice
    • Alternatives: Vancomycin and Ist Generation cephalosporin (cefazolin)
  • For Gram-Negative rods:
    • Cefepime
    • Ceftazidime
  • For Gram-Negative cocci:
    • Aminoglycosides
    • Ceftriaxone
  • Neisseria gonorrhoeae
    • IV ceftriaxone
  • Chlamydia
    • Doxycycline