Osteoarthritis

Definition

Osteoarthritis (OA) is a degenerative joint disease characterized by progressive loss of articular cartilage, subchondral bone remodeling, and synovial inflammation, leading to pain, stiffness, and functional impairment.

Epidemiology

• Most common form of arthritis worldwide
• Prevalence increases with age, especially >50 years
• Slight female predominance, particularly postmenopausal women
• Affects weight-bearing joints: knees, hips, spine, and hands
• Incidence is rising with aging population and obesity epidemic
• Leading cause of chronic disability in adults
• Hereditary predisposition observed in some cases

Etiology

• Primary OA: age-related degeneration without identifiable cause
• Secondary OA: due to trauma, joint malalignment, obesity, or metabolic disorders
• Genetic predisposition influencing cartilage resilience
• Mechanical stress from repetitive use or injury
• Obesity increases joint load and inflammatory mediators
• Post-traumatic changes after fractures or ligament injuries
• Joint instability or congenital malformations contributing to degeneration

Pathophysiology

• Cartilage matrix degradation due to imbalance between synthesis and breakdown
• Chondrocyte dysfunction and apoptosis
• Subchondral bone sclerosis and osteophyte formation
• Synovial inflammation contributing to pain and stiffness
• Joint space narrowing and altered biomechanics
• Progressive loss of joint function and deformity
• Inflammatory mediators (IL-1, TNF-α) accelerate cartilage destruction