Osteoarthritis

Osteoarthritis, also known as degenerative joint disease, is the most common form of arthritis and a leading cause of disability worldwide. The incidence of osteoarthritis increases with age, and disproportionately affects women. Individuals younger than 55 years of age have an equal distribution of affected joints regardless of gender; in older individuals, hip osteoarthritis is more common in men. Racial differences exist in the incidence of hip osteoarthritis as well with a greater incidence in whites as compared to the Hong Kong Chinese, for example. The risk for disability as a result of osteoarthritis is as great as that attributable to cardiovascular disease.

The primary physical effects of osteoarthritis are the symptoms of pain. The joint pain of osteoarthritis is described as a deep aching sensation present in the involved joint. Generally, movement of the involved [Page 1298]joint provokes the pain which will be relieved by rest. With progression of the disease, the pain may become persistent. Such advanced disease may be responsible for nocturnal pain and sleep interference, particularly in advanced osteoarthritis of the hip.

The cause of the pain is generally due to an inflammatory response secondary to damaged tissue. The foremost feature of osteoarthritis is the progressive erosion of articular cartilage. The cartilage will become soft, frayed, and progressively thinned. Eventually, the exposed bone (subchondral) will convert to a more dense substance with a smooth surface, a process known as eburnation. Simultaneously, there will be bony protuberant outgrowths, known as osteophytes, from the bone margins, ultimately leading to pain and loss of function as a result. The joint destruction may become significant enough to lead to joint incongruity.

Osteoarthritis mainly affects weight-bearing joints, and is more common in overweight and older persons. While the most prominent of the changes take place in the load-bearing areas of the cartilage, smaller joints may be affected that may not have served as predominant load-absorbing joints. It was previously believed that osteoarthritis involved only the joint. Research has shown that the disorder is one of the whole joint organ. Gross alterations do take place at a macroscopic level, while the underlying pathology is now known to involve the synovium, capsule, and the bone beneath the cartilage as much as the cartilage itself.

The progression of scientific understanding has changed the view of osteoarthritis as solely representing a wear and tear of damaged and overused joints. Changes in understanding have led to a shift in the paradigm of osteoarthritis which was once seen only as a passive, degenerative disorder for which little can be done. The realization that osteoarthritis is driven by an active disease process of the joint that can be modified by both mechanical and biochemical manipulations will undoubtedly improve the quality of life of patients suffering from the disease. The metabolically active role of the disease process is now recognized. Research suggests that it may be possible to arrest the progress of and, potentially, even reverse the disease.

The reasons for differing subjective measures of pain levels by individual patients with similar conditions are still unknown. In addition, there are often no parallels between symptoms and clinical signs of osteoarthritis and the presence of radiographic signs of osteoarthritis. At present, there is no specific or universally applicable criterion by which to measure the impact of osteoarthritis. Numerous sources give estimates of the prevalence of arthritis, prevalence estimates of arthritis range from as low as 6 percent of the adult population in the United States to as high as 90 percent of the population over age 40.

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