Septic Arthritis

Inflammation of the joint space caused by infection

Aetiology

Causative organisms

  • Staphylococcus aureus ‐ the most common cause in adults
  • Streptococci ‐ the second most common cause
  • Haemophilus influenzae ‐ was the most common cause in children but is now uncommon in areas where Haemophilus vaccination is practiced
  • Neisseria gonorrhoea ‐ in young adults (now thought rare in Western Europe)
  • Escherichia coli ‐ in the elderly, IV drug users and the seriously ill

Pathophysiology

  • Haematogenous spread (most commonly)
  • Can be an extension of local infection
  • Suppurative
  • Orthopaedic emergency due to rapid irreversible damage to hyaline articular cartilage

Clinical presentation

Symptoms

  • Typically presents as an acute monoarthropathy - single warm, red, painful joint with pain whenever the joint moves
    • Any joint that is hot, red and tender is a septic joint until proven otherwise - must aspirate
  • Knee most commonly affected joint

Signs

  • Reduced ROM +/- swelling
  • Patients may have systemic fever

Investigations

  • Aspiration of joint fluid - microscopy, culture, sensitivity
  • Bloods - CRP may be raised, blood culture if pyrexial (positive in 30-60% of cases)
  • Exclude crystals e.g. gout
  • X ray, consider MRI

Management

  • Avoid empirical antibiotics if patient is not septic
    • If septic - flucloxacillin, if under 5 add ceftrioxine (for H. influenzae cover)
    • Adjust when organisms confirmed
  • Once culture comes back: 1-2 weeks IV antibiotics to cultured organism, may require joint washout, if good progress PO antibiotics til 6 weeks antibiotics completed
  • Response to treatment is based on clinical findings and serial CRP