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Drugs for knee osteoarthritis: What primary care physicians need to know -- A clear understanding of the symptoms and treatment options is required.

Article Excerpt
Byline: NATHAN URQUHART, WILLIAM D. STANISH, MD

ABSTRACT: The prevalence of knee osteoarthritis (OA) is high, and it often results in pain and limited function. Primary care physicians need a clear understanding of the symptoms and treatment options because most patients with knee OA present to them. The view of OA has shifted to that of both a local and systemic condition in which inflammation plays an important role. A detailed history is the most important diagnostic tool. Nonpharmaceutical approaches to treatment include patient education, weight reduction, exercise, and bracing. Acetaminophen and NSAIDs are the most frequently used pharmaceutical agents. Glucosamine and chondroitin sulfate provide an alternative treatment approach. Intra-articular injection of corticosteroids or of hyaluronic acid may be beneficial. Total joint replacement is the definitive surgical intervention. (J Musculoskel Med. 2007;24:178-187)

Osteoarthritis (OA) is by far the most common musculoskeletal disorder worldwide.1 In the United States, an estimated 40 million persons (15% of the population) have arthritis.2 In Canada, the self-reported prevalence of arthritis in persons older than 15 years-16%, or nearly 4 million persons-is predicted to increase to 20.6% during the next 25 years.3

Moderate to severe OA can have a significant impact on patients' ability to carry out activities of daily living. The joints most often affected by OA are the knees, hips, hands, and spine; knee OA is of major concern because its prevalence is high and it often results in pain and limited function.

Only a small number of patients with knee OA see a specialist.4 Therefore, primary care physicians need to be prepared for patients by developing a clear understanding of the symptoms and treatment options. The diagnosis should be based primarily on clinical findings and radiological evidence. Nonpharmaceutical interventions should be tried first, but pharmaceutical products often are used if there is a significant disease flare-up.

In this article, we discuss the importance of making an accurate diagnosis of OA and provide a framework for counseling patients on symptom management. We review guidelines for lifestyle-modification, pharmaceutical, and surgical interventions, emphasizing the use of pharmaceutical products. Although we focus on knee OA, many of the treatments may be applied to other affected joints.

PATHOPHYSIOLOGY

OA is a degenerative process associated with mechanical stress and biological factors. It is highlighted by the breakdown of articular cartilage in synovial joints, as well as changes in subchondral bone, joint synovium, and periarticular ligaments and muscles (Figure 1). OA also is a dynamic process of repair and destruction as the body attempts to stabilize and reduce stress across joint surfaces, eventually resulting in joint failure.5

To understand the pathophysiology of OA, a physician must first gain an appreciation of the anatomy and chemistry of synovial joints.

Articular cartilage covers the ends, allowing for smooth joint motion by reducing friction and absorbing shock (Figure 2). This cartilage is composed of chondrocytes suspended in a macromolecular matrix of collagen and proteoglycans; type II is the primary type of collagen.6

Cartilage has a high water content, which provides stiffness and durability as well as elastic properties and dynamic compressibility, allowing for the smooth motion and shock absorption required in weight-bearing joints.6 A biochemical milieu of factors secreted by articular and periarticular tissues maintains this matrix. These chemical factors regulate regeneration and breakdown; they are influenced by aging, disease, and joint trauma.7 Complicating articular cartilage regeneration is a lack of nerves and blood vessels and heavy reliance on diffusion for nutrients.

Traditionally, OA has been viewed as a localized, noninflammatory degenerative disease process, in contrast to rheumatoid arthritis (RA), which is considered a systemic, inflammatory disease. In recent years, however, the view of OA has shifted to that of both a local and systemic condition in which inflammation plays an important part in determining the symptoms and...