Septic Arthritis

Question 1

Septic arthritis is a medical emergency !!!

Answer 1

Consider septic arthritis in ANY ACUTELY inflamed joint because septic arthritis can destroy a joint in <24h

Question 2

What is the route of spread for septic arthritis?

Answer 2

Septic arthritis occurs:

i. Directly via injury to the joint
ii. Blood borne infections from an infected lesions

Question 3

What is the mortality rate for septic arthritis?

Answer 3

11% mortality rate

Question 4

What are the risk factors for septic arthritis?

Answer 4

Pre-existing joint disease especially rheumatoid arthritis

Diabetes

Immunosuppression

Chronic renal failure

Recent joint surgery

Prosthetic joint (difficult to treat infection)

IV drug abuse

> 80 years old

Question 5

What is the clinical presentation of septic arthritis?

Answer 5

In young and healthy patients:

=> Red, hot, swollen joints
=> Agonisingly painful
=> Immobile due to muscle spasm

In elderly, immunosuppressed and patients with rheumatoid arthritis:

=> Insidious onset
=> Lack of systemic symptoms

*In 20% of patients, multiple joints are affected

Question 6

Which organisms most commonly causes septic arthritis?

Answer 6

Staphylococcus aureus => most common & in neonates

Other organisms:
=> Streptococci
=> N. Gonorrhoeae (35 year old and sexual history)
=> Gram -ve bacilli

Question 7

How do you investigate for septic arthritis?

Answer 7

1. Urgent joint aspiration (arthrocentesis) for synovial fluid microscopy and culture
   * joint aspiration is essential in any mono-arthritic presentation

Do not aspirate over inflamed or infected skin i.e. psoriatic plague or cellulitis OR Do not aspirate if non-native joint (knee replacement) - go straight to theatre

2. Bloods: CRP (may be normal), leukocytosis, cultures if sepsis
3. X-ray

Question 8

What is the differential diagnosis for septic arthritis?

Answer 8

Crystal arthropathies i.e. gout and calcium pyrophosphate

Question 9

How do you treat septic arthritis?

Answer 9

=> Emergency surgical drainage and irrigation of the joint

=> If in doubt start empirical antibiotics (after aspiration) until sensitives are known

=> Local guideline for antibiotic choices

=> Antibiotics needed for a prolonged period i.e. 2 weeks IV then 2-4 weeks orally