Septic Arthritis (2*)

Question 1

Why is it a medical emergency?

What is the most common cause?
→ What are some of the other causes?

What are its differentials?

Answer 1

➊ Infection can quickly destroy the joint and cause serious systemic illness

➋ Staph aureus
→ Neisseria gonorrhoea (in sexually active teens), Group A strep, E.coli

➌ Transient Synovitis, JIA, Perthes disease, Slipped upper femoral epiphysis
• Transient synovitis presents very similarly to early SA, but has much milder symptoms

Question 2

How does it present?

Answer 2

• Painful, swollen, hot, red knee
• Resistance to attempted movement of joint
• Signs can be subtle in young children, so always consider this as a differential in a child presenting with joint problems, esp. if in pain and refuse to move it

Question 3

How is it investigated?

How is it managed?

Answer 3

➊ * Bloods – WCC, CRP, ESR
* Imaging – Joint US, XR, MRI
* Joint Aspiration and MC&S

N.B. Gram stain is positive in ~50% of cases, so a negative gram stain doesn’t rule out infection.

➋ * Urgent washout of joint
* IV Abx – Starting with broad-spectrum until sensitivities known