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()Map MUSCULOSKELETAL SYSTEM (Map)
JOINTS



Arthritis

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


Infectious arthritis

  • Bacterial arthritis
    • Most common in food animals, especially young
    • Portals of entry include:
      • Navel and GI tract -> bacteraemia
      • Haematogenously -> polyarthritis
      • Traumatic inoculation
      • Extension from bone or periarticular soft tissue
  • Viral arthritis
    • Progressive inflammatory and degenerative joint disease
    • Synovitis with cartilage destruction
    • Chronic mononuclear inflammatory reactions


In Sheep

In Pigs

  • Erysipelothrix rhusiopathiae
    • Most important and most common cause of arthritis
    • Causes chronic serofibrinous polyarthritis
    • Also causes discospondylitis
    • Thickening of synovial membrane lining + plus hyperaemia and villus formation + lymphocyte and plasma cell infiltration
    • Acute stage
      • Increased joint fluid + hot swollen joints
      • Also expresses as septicaemic and urticarial lesion on the back (diamond shaped)
      • May involve endocarditis as a sequel
    • Chronic stage
      • More commonly encountered
      • Erosion of articular surface of joints with formation of pannus +/- joint ankylosis
      • Vaccination prevents septicaemic and urticarial forms but has no effect on joints
        • Probably due to dead bacteria still stimulating host immune system
    • Septicaemia lo9calises in meninges and joints
    • Well known in piglets in their first two months of life
    • Expresses as acute fibrinopurulent arthritis
  • Corynebacterium pyogenes and Staphylococci
    • Cause purulent arthritis
    • In one or more joints
    • Commonly contaminate wounds
  • Haemophilus suis and Haemophilus parasuis
    • Cause Glasser's disease
    • Fibrinous polyserositis, polyarhritis, meningitis
  • Mycoplasma hyosynoviae and M. hyorhinis
    • Produce syndrome similar to Glasser's disease with milder expression
    • Menigitis is rare
    • Arthritis most consistent

In Cattle

  • Neonatal polyarthritis by:
    • Streptococcus spp.
      • Via umbilicus
      • Also involves eyes and meninges
    • Coliforms
      • Localises in joints and meninges in sevee non-fatal neonatal colibacillosis
      • May remain as chronic arthritis in larger joints
  • Infections at any age:
    • Corynebacterium pyogenes
      • Suppurative arthrtis
      • Often due to pebetrating wound into or close to joints
    • Mycoplasma spp.
      • May be respinsible for some chronic cases but difficult to prove as hard to isolate
      • Fibrinous polyarthritis
    • Chlamydia sp.
      • Severe disease in young calves
      • High mortality
      • Can be seen in smears of synovial fluid from swollen joints
      • Oedematous and hyperaemic surrounding tissue
      • Possibly due to intrauterine infection
    • Brucella abortus
      • Uncommonly localises in joints
      • Usually in carpal bursitis (hygroma) in cattle and bursitis in horses


In Horses


In Goats

  • Caprine Arthrirtis Encephalitis Virus
    • Arthritis is commonly the main expression
    • Large limb joints are thickened
    • Carpal hygroma is often present
      • Subcutaneous cystic swelling on cranial surface of the knee, contains serous fluid
    • In advanced cases
      • Synovial villus hypertrophy
      • Necrosis
      • Mineralisation
      • Mononuclear cell infiltration
      • Pannus formation
      • Articular cartilage destruction

In Dogs


Non-infectious arthritis

  • No causative agent has been found
  • Seem to be immune-mediated diseases


Erosive

Rheumatoid arthritis

  • Occurs in the dog, mainly smaller breeds
  • Uncommon
  • Progressive erosive polyarthritis
  • Mostly involves elbows, stifles, carpal and tarsal joints
  • Grossly:
  • Histologically:
    • Hyperplasia of lining cells
    • Proliferative synovitis
    • Synovial membrane has fibrin deposits
    • Lymphoid and plasma cell infiltration
    • Surrounding haemorrhagic areas
    • Macrophages containing haemosiderin
    • Connective tissue may contain foci of necrosis
    • Areas of erosion of peripheral articular cartilage and underlying subchondral bone
  • Pathogenesis:
    • May involve deposition of immune complexes within joints
    • Substances degrading cartilage are released by synovial cells and macrophages involved in pannus formation


Non-erosive

Systemic lupus erythematosus (SLE)


In chronic diseases


Gout

  • Occurs in humans, reptiles and birds (have no uricase enzyme)
  • The urate triggers inflammation