Joint Response to Injury

Causes of injury

• Trauma
• Instability
• Lubrication failure
• Infectious organisms
• Immune-mediated disease

Reaction to injury

• Articular cartilage has limited ability to regenerate
  • Superficial defects are long standing
    • Chondrocyte hyperplasia is ineffective at filling the defect
    • Non-painful
  • Defects reaching subchondral bone
    • Filled with vascular fibroous tissue undergoing metaplasia into cartilage
    • Painful
  • Fibrillation - loss of proteoglycans -> condensation of collagen fibres -> fraying of surface
  • Eburnation - loss of articular cartilage -> exposure of subchondral bone -> becomes dense and polished
• Synovial membranes respond by:
  • Villous hypertrophy
    • +/- synovitis
  • Hyperplasia