Osteoarthritis

OSTEOARTHRITIS

Osteoarthritis (OA) (degenerative joint disease) is joint degeneration with loss of articular cartilage, with no to minimal inflammation. It is the most common form of arthritis. Risk increases with age; OA affects at least 1 joint in 80% of people age >70.

Clinically, there is an insidious onset of joint stiffness; deep, aching joint pain, which worsens with repetitive motion; decreased range of motion; crepitus; and joint effu-sions and swelling. Osteophytes may cause nerve compression. X-ray studies show narrowing of the joint space due to loss of cartilage; osteosclerosis and bone cysts; and osteophytes (osteophytic lipping).

The pathogenesis involves both biomechanical factors (aging or wear and tear of articular cartilage) and biochemical factors (chondrocyte injury and abnormal colla-gen activity). Predisposing factors include obesity, previous joint injury, ochronosis, diabetes, and hemarthrosis.

OA affects weight-bearing joints (knees, hips, and spine), often with asymmetrical involvement.

•         There is degeneration and loss of articular cartilage with eburnation (exposed bone becomes polished) and subchondral bone sclerosis.

•         The changes may include subchondral bone cysts, loose bodies (joint mice), which are free-floating fragments of cartilage and bone, and osteophytes (bone spurs), which are reactive bony outgrowths.

•         Heberden nodes are osteophytes at the distal interphalangeal (DIP) joints, while Bouchard nodes are osteophytes at the proximal interphalangeal (PIP) joints.