Septic Arthritis

Question 1

Define septic arthritis.

Answer 1

Septic arthritis is defined as the infection of 1 or more joints caused by pathogenic inoculation of microbes. It occurs either by direct inoculation or via haematogenous spread.

Question 2

Explain the aetiology/risk factors of septic arthritis.

Answer 2

Underlying joint disease
Joint prostheses
Intravenous drug abuse
Diabetes
Presence of cutaneous ulcers

Question 3

Summarise the epidemiology of septic arthritis.

Answer 3

The estimated incidence of septic arthritis in developed countries is 6 cases per 100,000 population per year. In patients with underlying joint disease or with prosthetic joints the incidence increases approximately 10-fold, to 70 cases per 100,000 of the population.

Question 4

Recognise the presenting symptoms of septic arthritis. Recognise the signs of septic arthritis on physical examination.

Answer 4

Hot, swollen, tender, restricted joint
Fever

Question 5

Identify appropriate investigations for septic arthritis and interpret the results.

Answer 5

Synovial fluid Gram stain and culture
Synovial fluid white cell count
Blood culture
White cell count
Erythrocyte sedimentation rate
CRP
Plain radiograph
Ultrasound