Arthritis Classification

Fibrinopurulent arthritis in cattle (Image sourced from Bristol Biomed Image Archive with permission)

Suppurative arthritis in cattle (Image sourced from Bristol Biomed Image Archive with permission)

• Inflammation of intra-articular structures
• In farm animals usually due to infection
• In small animals usually due to non-infectious causes

• Classification:
  • According to number of joints involved - polyarthritis
  • According to type of inflammatory exudate
    • Serous
      • Increased synovial fluid production
      • Resolves if uncomplicated
    • Fibrinous
      • Early stages:
        • Increased and more opaque synovial exudate
        • Enlarged hyperaemic villi
        • Small haemorrhages in synovial membrane
      • Later stages:
        • Less exudate
        • Thickend synovial connective tissue
        • Marked villi proliferation (branching in microscopic preparations)
        • Proliferated synovial tissue -> peripheral fibrous tissue attempting repair across defective surface = pannus
      • Mild cases resolve
      • More severe cases - residual inflammation remains
      • Most severe cases - organising fibrosis +/- ankylosis
    • Purulent
      • Usually from haemoatogenous spread e.g. neonatal navel ill
      • May extend from adjacent abscesses
      • More destructive
      • Erosion of articular surfaces to underlying bone
      • Forms abscesses
      • Possible fistulation to the skin

• Caused by:
  • Trauma
  • Infectious organisms (e.g. bacteria, viruses)
  • Foreign material (urate crystals = gout)
  • Immune-mediated disease