Septic arthritis

• Septic Arthritis

  A serious (emergent) and painful infection of a body joint
• Pathophysiology of Septic Arthritis

  1. Three routes of bacterial seeding of joint: Bacteremia "hematogenous", Direct inoculation, From trauma or surgery, Contiguous spread, From adjacent osteomyelitis

  2. Septic arthritis causes irreversible cartilage destruction in an involved joint, Cartilage injury can occur by 8 hours, Caused by release of proteolytic enzymes from inflammatory cells (PMNs)
• Risk Factors for Septic Arthritis

  • Age > 80 years, Medical conditions (Diabetes, Rheumatoid arthritis, Cirrhosis or HIV), History of crystal arthropathy "gout", Endocarditis or recent bacteremia, IV drug user, Recent joint surgery
• Presentation of Septic Arthritis

  1. Symptoms include pain in affected joint, Fever (present in 60% of cases), May appear toxic

  2. Physical exam shows inspection findings like Erythema, Effusion, Extremity position, Palpation findings of Warmth & Tenderness, Motion findings of Inability to bear weight, Inability to tolerate Passive Range Of Motion
• Kocher Criteria for Septic Arthritis


  • WBC > 12,000 cells/µl of serum, Inability to bear weight, Fever > 101.3° F (38.5° C), ESR > 40 mm/h
• Kocher Criteria and likelihood of septic arthritis

  0 criteria → <0.2% to have septic arthritis, 1 criteria → 3% to have septic arthritis, 2 criteria → 40% to have septic arthritis, 3 criteria → 93% to have septic arthritis, 4 criteria → 99.6% to have septic arthritis
• Distinguishing septic arthritis from transient synovitis is based on meeting the Kocher Criteria
• Investigations for Septic Arthritis

  Serum labs: WBC >10K with left shift
• Criteria for septic arthritis

  • 3% to have septic arthritis if meet 1 criteria
  • 40% to have septic arthritis if meet 2 criteria
  • 93% to have septic arthritis if meet 3 criteria
  • 99.6% to have septic arthritis if meet 4 criteria
• Distinguishing septic arthritis from transient synovitis is important
• Investigations

  1. Serum labs: WBC>10K with left shift, ESR>30 (often elevated but may be normal early in process, rises within 2 days of infection), CRP>5 (most helpful, rises within few hours of infection, may normalize within 1 week of treatment)

  2. Radiographs: X-RAY (AP and lateral of the joint in question findings, show joint space widening), ULTRASOUND (may help in confirming joint effusion in large joint such as hip, can be used in guiding aspirations), MRI (detects joint effusion, may detect adjacent bone involvement such as osteomyelitis)
• Joint fluid aspiration

  Gold standard for treatment & allows directed antibiotic treatment, should be analyzed for: Cell count with differential, Gram stain & Culture, Glucose level, Crystal analysis
• Prosthetic joint with WBC >1,100 is considered septic
• Glucose less than 50-60% of serum level indicates septic arthritis
• Management of septic arthritis

  Septic arthritis is an emergency, IV antibiotic therapy, Operative irrigation and drainage of the joint, Treatment monitoring by following serum WBC, ESR, and CRP levels, Patients need good rehabilitation and physiotherapy post drainage
• Complications of septic arthritis

  • Arthritis, Osteomyelitis