CBL - Septic Arthritis

Question 1

List the important predisposing risk factors for septic arthritis [7]

Answer 1

1. Increasing age
2. Pre-existing joint disease
3. Recent joint surgery or injection
4. Skin or soft tissue infection
5. Intravenous drug use
6. Indwelling catheters
7. Immunosuppression (including diabetes)

Question 2

Describe the pathophysiology of septic arthritis [5]

Answer 2

1. septic arthritis develops as a result of hematogenous seeding or direct inoculation of bacteria into the joint.
2. hematogenous seeding
   
   • the synovial membrane has no limiting basement membrane, allowing organisms to enter the joint space.
   • this is caused by organisms that are able to adhere to the synovial tissues e.g. Staphylococcus aureus
3. direct inoculation of bacteria into the joint
   
   • mechanisms include trauma, arthroscopy or other surgery, and intra-articular injection

Question 3

What are the most common bacterial causes of septic arthritis in an adult? [3]

Answer 3

1. Staphylococcus aureus
2. Streptococci/Strep pneumoniae (less common)

Question 4

Septic arthritis due to gram-negative bacilli typically occurs in which types of patients? [4]

Answer 4

1. older adults
2. patients with underlying immunosuppression
3. intravenous drug users
4. as a complication of trauma

Question 5

List four important clinical signs/symptoms associated with acute septic arthritis [4]

Answer 5

1. Joint pain
2. Joint swelling
3. Warmth
4. Restricted movement

Question 6

What three key investigations are recommended to diagnose septic arthritis? [3]

Answer 6

1. Blood cultures
2. Imaging- X-ray, CT
3. Joint aspirate- for microscopy & culture

Question 7

What is the minimum total duration of antimicrobial therapy recommended for the treatment of septic arthritis? [3]

Answer 7

1. at least 14 days of parental (IV) therapy,
2. followed by oral therapy for an additional 7 to 21 days.
3. The choice of oral antibiotic regimen for completion of therapy depends on:
   
   • the pathogen
   • antibiotic susceptibility (oral agents with high bioavailability)