Canine Degenerative Joint Disease Study Guide

Overview and Clinical Importance

Degenerative joint disease (DJD), also known as osteoarthritis (OA), is a chronic, progressive condition of synovial joints characterized by articular cartilage degeneration, periarticular osteophyte formation, subchondral bone changes, and synovial inflammation. It affects approximately 20% of dogs over one year of age. In dogs, OA is most commonly secondary to developmental orthopedic diseases (hip/elbow dysplasia, OCD), traumatic injuries (CCL rupture), or joint instability.

Etiology and Risk Factors

Classification of Osteoarthritis

Breed Predispositions

Modifiable and Non-Modifiable Risk Factors

Pathophysiology

Normal Joint Structure

A healthy synovial joint consists of articular cartilage (hyaline, 2-4 mm thick, avascular/aneural), extracellular matrix (Type II collagen, proteoglycans/aggrecan, 60-80% water), synovial membrane (produces synovial fluid), and subchondral bone (provides structural support).

Pathogenesis of Cartilage Degeneration

OA is a disease of the entire joint organ. The pathogenesis involves mechanical and biological factors in a progressive cascade.