Septic Arthritis

 

• Background

  • Bacterial infection of a joint.
  • Can rapidly destroy the joint.
  • Common pathogens: Staph. aureus, N. gonorrhoeae, Gram -ve bacilli.

• Signs and symptoms

  Septic joint:

  • Acute monoarthritis: hot, red, swollen, painful joint. May be immobile.
  • Most commonly affects knee.
  • Fever, systemically unwell.

  Gonococcal arthritis may follow a mucosal infection (genital, rectal, or pharyngeal) and can present in 2 ways:

  • Septic monoarthritis. Typically milder than S. aureus arthritis.
  • Arthritis-dermatitis syndrome: classic triad of rash (papular or pustular), tenosynovitis (dorsum of hand, ankles or knees), and migratory polyarthritis (upper > lower limbs).

• Risk factors

  • RA
  • Diabetes
  • Immunosuppression
  • Kidney failure.
  • Joint replacement.

• Investigations

  Bloods and microbiology:

  • FBC and CRP.
  • Join aspiration: Gram stain and culture.
  • Blood culture.
  • In suspected gonococcal arthritis, get urethral, rectal, and throat swabs to maximize chance of positive culture, as joint aspiration often negative (especially in arthritis-dermatitis).

  Imaging:

  • X-ray should be done, but is often normal.
  • CT and MRI is more sensitive but only used if there is diagnostic uncertainty.

• Management

  • Antibiotics for 4-6 weeks, initially IV for 2 weeks. Flucloxacillin for Staph. aureus, vancomycin for MRSA, or cefotaxime for N. gonorrhoeae or Gram -ve bacilli. Start after joint aspiration.
  • Drainage of joint if severe. This may involve serial aspirations if the joint is easily accessible (e.g. knee, elbow), or open washout in theatre if less accessible (e.g. hip).
  • Splinting