Bone and Joint pathology

Response to injury (limited)

Inflammation

Degeneration

Degenerative Joint Disease

IV disk degeneration

Osteochondrosis drecans

Infectious arthritis

Bacterial

Synovitis

Extent

Subchondral bone involvement

Vascular fibrous tissue infiltration

Metaplasia --> fibrocartilage

Superficial cartilage involvement

Inflammatory

Persistent defects

Synovitis

Hyperaemia; inflammatory oedema

Degrade collagen/proteoglycan

Fibrillation (clefts)

↪ further cartilage loss

➡ eburnation

Degenerative

Villous hypertrophy + hyperplasia

Hyaluronic acid degradation

Loss of lubricating properties

Pannus formation

Fibrovascular histiocytic tissue

Promote destruction of underlying cartilage

Glucocorticoids 🚫

⬇ Synthesis of cartilaginous matrix

⬇ Mechanical strength

⬆ Proteoglycans depletion

Causes

Trauma

Chronic, low grade

Unstable joints

Eg. Hip dysplasia; ruptured cruciate ligament (stifle)

Pathogenesis

⬆ periosteum bone formation around joints

Altered socket conformation

Mismatched coverage of bone head

Haematogenous; direct extension

Immune-mediated

Eg. Actinobacillus; erysipelothrix; e.coli

Pathogenesis

"Wobble syndrome"

Focal failure of endochondral ossification

Degeneration of overlying articular cartilage

Types

Serous; fibrinous; purulent; chronic (lymphoplasmacytic)

Viral

Encephalitis virus

Erysipelas (superficial cellulitis)

Ataxia due to vertebral column malformation

Articular-epiphyseal cartilage complex separation from epiphyseal bone

Humeral head 🐕

Slow healing

➡ DJD

Subchondral bone cysts

Predispostition

Young, fast growing males

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