Septic Arthritis

Question 1

Define septic arthritis

Answer 1

Septic arthritis is defined as the infection of 1 or more joints caused by pathogenic microbes.

Question 2

What are the causes/risk factors of septic arthritis?

Answer 2

• It occurs either by direct inoculation or via haematogenous spread.
• The predominant causative organisms of septic arthritis are staphylococci or streptococci. These organisms account for 91% of cases.

• younger patients - more likely gonorrhoea and chlamydia

Risk Factors:
• Hx of RA and OA. 
• Joint prosthesis 
• DM 
• Immunosuppression 
• IVDU 
• Alcoholism 
• Intra-articular corticosteroid injections

Question 3

What are the symptoms of septic arthritis?

Answer 3

• Acute onset hot, swollen, painful joint
• Associated with restriction of movement.
• The knee is affected in > 50% of cases
• Presentation may be more insidious in the context of a low-virulence organism, TB, or if the joint is prosthetic.
• Usually monoarticular but can be polyarticular in up to 22%

Question 4

What are the signs of septic arthritis?

Answer 4

• The characteristic features of an infected joint are swelling, warmth, tenderness, and a significant reduction in the range of movement.
• The presence or absence of a fever is not a reliable indicator of joint sepsis

Question 5

What investigations are carried out for septic arthritis?

Answer 5

• Urgent joint aspiration for synovial fluid microscopy and culture is the key investigation. PCR for viral
- CI - Prosthetic joint –sterile procedure in OR should be done with orthopaedic surgeons.
• Blood cultures may be helpful for guiding antibiotic choice later.
• Plain Radiographs –may reveal underlying joint disease but otherwise normal.
• CRP/ ESR –Elevated but may be normal
• The main differential diagnoses are the crystal arthropathies