Septic Arthritis

Question 1

Define Septic Arthritis

Answer 1

Septic (infectious) arthritis is defined as the infection of 1 or more joints caused by pathogenic inoculation of microbes. It occurs either by direct inoculation or via haematogenous spread

Question 2

Explain the aetiology/risk factors of Septic Arthritis

Answer 2

Septic arthritis is caused by the pathogenic inoculation of micro-organisms into the joint, either directly or by the haematogenous route. The predominant causative organisms of septic arthritis are staphylococci or streptococci. These organisms account for 91% of cases.

Risk factors for the development of joint sepsis include:

• Haematogenous spread (MOST COMMON)
  
  • Other causes of infection, such as skin infections/IVDU - can lead to bacteraemia and subsequent seeding of infection in a joint
• Prosthetic joint (staph epidermidis is common in this case)
• Underlying joint disease
  
  • Osteoarthritis
  • Rheumatoid arthritis
• Sexually active youngsters (N. gonorrhea infection ➔ disseminated gonococcal infection)
• Immunosuppression
  
  • HIV
  • Diabetes
  • Alcohol misuse
  • Immunosuppressive medication
  • Chemotherapy
• Exposure to ticks may indicate arthritis associated with Lyme disease.

Question 3

Recognise the presenting symptoms

Answer 3

• Acutely (<2 weeks) swollen, red, warm and painful joint - this presentation is septic arthritis until proved otherwise
  
  • There is restricted motion about the joint
  • Mostly Monoarticular and at large joints (most commonly the knee > hips, shoulder, elbow, wrist, ankle)
• Fever (57% so not very sensitive)

Question 4

Recognise the signs on physical examination

Answer 4

• Hot, swollen, red joint
• Erythema migrans (if Lyme disease)
• Reduced ROM about joint

Question 5

Investigations

Answer 5

• ARTHROCENTESIS for synovial fluid analysis:
  
  • Synovial fluid Polarising microscopy: no crystals
  • Synovial MCS & Gram Stain: identify organism
  • Synovial fluid WCC and apperance: significant neutrophilia & turbid
• Blood culture and sensitivities (before giving ABx) in case of haematogenous spread
• FBC: Raised WCC (neutrophillia)
• CRP: Raised

Question 6

Management

Answer 6

DO NOT GIVE STEROIDS

Resuscitation

• IV Flucloxacillin is first line ➔ AFTER cultures have been taken (change depending on sensitivities)
  
  • usually taken for 6 weeks, oral stepdown occurs after 2 weeks
• Analgesia (paracetamol, NSAIDs ➔ WHO pain ladder)

SURGICAL

• Arthroscopic joint washout
• Fluid/effusion drainage