Excerpt from Osteoarthritis

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Background

Osteoarthritis (OA) is the most common articular disease worldwide, affecting over 20 million individuals in the United States alone. Its high prevalence entails significant costs to society. Direct costs of osteoarthritis include clinician visits, medications, and surgical intervention. Indirect costs include such items as time lost from work. Costs associated with osteoarthritis can be particularly significant for elderly persons, who face potential loss of independence and who may need help with daily living activities. As the populations of developed nations age over the next few decades, the need for better understanding of osteoarthritis and for improved therapeutic alternatives will continue to grow.

Pathophysiology

Traditionally, osteoarthritis has been considered a disease of articular cartilage. The current concept holds that osteoarthritis involves the entire joint organ, including the subchondral bone and synovium.

Osteoarthritis has always been classified as a noninflammatory arthritis; however, increasing evidence has shown that inflammation occurs as cytokines and metalloproteinases are released into the joint. Therefore, the term degenerative joint disease is no longer appropriate when referring to osteoarthritis.

Osteoarthritis predominantly involves the weight-bearing joints, including the knees, hips, cervical and lumbosacral spine, and feet. Other commonly affected joints include the distal interphalangeal (DIP) and proximal interphalangeal (PIP) joints of the hands.

Cartilage is grossly affected. Focal ulcerations eventually lead to cartilage loss and eburnation. Subchondral bone formation also occurs, with development of bony osteophytes.

Frequency

United States

Osteoarthritis affects over 20 million individuals in the United States. Based on the radiologic definition of osteoarthritis, more than half of adults older than 65 years are affected.

International

Osteoarthritis is the most common articular disease. Estimates vary among different populations.

Mortality/Morbidity

• The disease progression of osteoarthritis is characteristically slow, occurring over several years or decades.
• Pain is usually the initial and principal source of morbidity in osteoarthritis. The patient can become progressively less active, leading to morbidities related to decreasing physical activity (including potential weight gain).

Race

The prevalence of osteoarthritis differs among different ethnic groups. Knee osteoarthritis appears to be more common in African American women than in other groups.

Sex

• The likelihood of developing osteoarthritis increases with age. The disease is equally common among men and women aged 45-55 years. After age 55 years, the disease becomes more common in women.
• DIP and PIP joint involvement that results in Heberden and Bouchard nodes is more common in women.

Age

• Osteoarthritis can be defined epidemiologically (ie, using radiographic criteria) or clinically (eg, radiography findings plus clinical symptoms). Based on radiographic criteria, osteoarthritis occurs in 30% of affected individuals aged 45-65 years and in more than 80% by their eighth decade of life, although most are asymptomatic.

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