Septic Arthritis (infectious pyogenic arthritis, suppurative arthritis) – infection of joint cavity (synovium)

• 50% mortality; all survivors are crippled
• X-rays not helpful, aspiration is diagnostic
• Etiology: Neonates – Strep, Staph, Gram -, Haemophilus influenza
• Children – Staph aureus
• Teens – Gonorrhea
• Sources of infectious spread include:
• (1) Direct innoculation – joint penetration
• (2) Contiguous Spread – direct spread from surrounding skin/sub-cutaneous tissue infection or from osteomyelitis
• (3) Hematogenous seeding
• Pathology: acute inflammation and hyperemia of synovium. Articular cartilage may be damaged because of acute inflammatory exudate. Mechanisms of damage include:
• Pressure necrosis and synovial hypertrophy - interruption of nutrition of cartilage
• Enzymes from bacteria and degenerating inflammatory cells – degrade matrix
• Enzymes from synovial cells – alter lubrication
• Histology: Destructive granulomatous process
• Clinical Manifestations: typically involves hips, ankles or knees in infants or neonates
• Neonates: Pseudoparalysis, erythema
• Kids: tenderness, acute pain , erythema, restricted range of motion
• X-ray: capsular destruction from swelling
• Treatment: Surgical emergency Þ immediate drainage (needle aspiration); inflamed synovium will attach to articular cartilage forming a Pannus (acute inflamed tissue growing over the articular cartilage and destroying it); antibiotics, debridement