Septic arthritis

Question 1

Define septic arthritis.

Answer 1

joint infection in either native or prosthetic joint.

medical emergency

Question 2

Causes of septic arthritis.

Answer 2

• Staph aureus is most common cause in adults.
• Neisseria gonorrhoea (gonococcus) in young sexually active individuals
  o N. gonorrhoea is gram neg. Ptx will present w/ urinary or genital symp – important to exclude septic arthritis.
• Group A Streptococcus (most commonly Streptococcus pyogenes)
• Salmonella – common in SCA
• Haemophilus influenza
• E. coli

Question 3

What are the methods by which bacteria can spread to the joint and cause septic arthritis?

Answer 3

• recent bacteremia (bac in blood) – e.g cellulitis, UTI or URTI.
• Direct inoculation (vaccine)
• Spread from adjacent osteomyelitis (infection of bone).

Question 4

Risk factors for septic arthritis

Answer 4

pre-existing joint disease - e.g RA
hip/ knee prosthetic
immunosuppression
DM
CKD
I.V drug use

Question 5

How does septic arthritis present?

Answer 5

signs:
- single swollen, red, hot, painful joint.
- tender
- extreme pain and unable to bear weight on joint
- visible effusion
- pain on active and passive movement, reduced ROM
- raised WCC, ESR

symp:
- systemically unwell - fever, lethargy, sepsis
- affected joint may be rigid

Question 6

How is septic arthritis diagnosed?

Answer 6

Low threshold

Ix:
- Bloods – FBC, CRP, ESR, urate levels.
- Blood cultures
- XRAY of joint
- A joint aspiration (US guided) –before Abx (unless ptx overly septic)
o If ptx has prosthetic joint- aspiration to be done in operating room.
o Joint fluid will appear – turbid and yellow (pus like).
o Joint fluid analysis should also be sent for Gram stain, WCC, polarising microscopy, and fluid culture.

Question 7

Management of septic arthritis

Answer 7

• Start IV empirical Abx until sensitivity results come back.
• Abx cont for 3-6 wks:
  o 1st – flucloxacillin + rifampicin
  o 2nd – vancomycin + rifampicin (if pen allergy, prosthetic joint or MRSA)
   Clindamycin alt
• Joint washout (irrigation and debridement) under GA – may be needed more than once.
• Physio after acute infection resolves

Question 8

Complications of septic arthritis

Answer 8

• Osteomyelitis
• OA
• Ankylosis fusion

Question 9

DDx list for a swollen, red, hot painful knee.

Answer 9

• septic arthritis
• gout
• pseudogout
• Reactive arthritis (riggered by urethritis or gastroenteritis and associated with conjunctivitis)
• Haemarthrosis
• RA
• Lyme disease