Epidemiology

Prevalence

Osteoarthritis (OA) is the most prevalent form of arthritis, one of the most common diseases affecting humans and a common cause of disability. It is estimated that as of 1998, more than 20 million Americans have symptomatic OA [Lawrence et al., 1998]. The prevalence of OA is expected to increase dramatically during the next 20 years as the population ages. In the United States, OA is second only to ischemic heart disease as a cause of work disability in men over age 50 [Lawrence et al., 1998]. OA is a major cause of disability in people aged 65 and older. Despite its public health impact, this disease continues to be a relatively unaddressed health issue.

In some people, evidence of osteoarthritic changes may exist by the second or third decade of life (usually without associated symptoms). By age 40, almost everyone has some osteoarthritic changes in weight-bearing joints (e.g., hip and knee joints) and, by age 75, virtually everyone has changes in at least one joint.

The reported prevalence of OA, however, varies according to the method that is used to detect it. X-rays are commonly used in the diagnosis of OA. However, marked osteoarthritic damage must be present to detect characteristic changes with radiologic imaging. More subtle damage may not be observed using this technique. Radiographic changes are seen in over half of all people older than age 65 with OA of the knee. In contrast, data obtained from autopsy studies indicate that there is almost universal evidence of osteoarthritic damage in people aged 65 and over [Dequeker and Dieppe, 1998; Kraus, 1997].

Radiographic Prevalence of OA by Age

In a population-based radiographic survey, 75% of women aged 60-70 had evidence of OA of the distal interphalangeal (DIP) joints of the hand. Although knee and hip OA were less prevalent, the prevalence rates of all joint sites studied increased markedly with age in both men and women [Dequeker and Dieppe, 1998].

Radiographic Prevalence by Gender

As shown in the following table, the distribution of OA in men and women is similar based on U.S. epidemiologic studies. According to these studies, radiographic evidence of OA of the knees is more common in women, whereas OA of the hips is more common in men. Smaller U.S. and European studies have shown a much higher prevalence of knee and hip OA, and a rereading of National Health and Nutrition Examination Survey (NHANES) I radiographs has suggested that prevalence may be up to fourfold higher than reported previously [Lawrence et al., 1998]; with permission.

Prevalence (per 100 persons) of Radiographic OA in Various Sites from Population-based Studies in the United States

Site Age (years) Mild, Moderate, and Severe OA

Male Female Total

Hands 25-74* 28.9† 30.1† 29.5†

Feet 25-74* 20.2† 21.4† 20.8†

Knees‡ 25-74** 2.4† 4.6† 3.5†

63-93*** 30.9 34.4 33.0

Hips 55-74** 3.5† 2.8† 3.2†

Data from *NHES=National Health Examination Survey 1960-1962, **NHANES I, 1971-1975, and ***Framingham Osteoarthritis Study 1983-1985. (See Lawrence et al. [1998] for further details.)
† Standardized to the 1990 U.S. population.
‡ All data on radiographic knee OA based on anteroposterior radiographs and, therefore, capture on tibiofemoral OA. Inclusion of patellofemoral imaging would probably yield higher prevalence estimates.
Adapted from Lawrence et al. [1998]; with permission.

Prevalence by Geography and Ethnicity

Although OA is worldwide in distribution, geographic and ethnic differences have been reported. For example, the prevalence of hand and knee OA is similar among Europeans and Americans. There is greater variation in the distribution of hip OA with markedly lower rates in African Blacks, Asian Indians, and Hong Kong Chinese. It has been suggested that the lower rates detected among these populations may be due to lower rates of congenital or developmental abnormalities and, in some cultures, the common use of squatting postures, which force the hip through extreme ranges of motion [Dequeker and Dieppe, 1998].

Incidence

Incidence of OA by Site and Gender

Incidence rates (1995) for hand, knee, and hip OA were obtained from a U.S. Health Maintenance Organization. The following figure illustrates the incidence of OA identified using radiography and joint symptoms. The incidence of symptomatic hand, hip, and knee OA increased with age and women had higher rates than men, especially after age 50. Around age 80, there was a leveling off or a decrease in the incidence of OA in both groups and all joint sites [Dequeker and Dieppe, 1998].

Incidence of OA

Data from Oliveria et al. [1995].
Click on image for larger version.

References

Dequeker J, Dieppe PA, eds. Disorders of bone cartilage and connective tissue. In: Klippel JH, Dieppe PA, eds. Rheumatology. 2nd ed. London: Mosby, 1998.

Kraus VB. Pathogenesis and treatment of osteoarthritis. Med Clin North Am. 1997; 81:85-112.

Lawrence RC, Helmick CG, Arnett FC, et al. Estimates of the prevalence of arthritis and selected musculoskeletal disorders in the United States. Arthritis Rheum. 1998;43:778-799.

Oliveria SA, Felson DT, Reed JI, et al. Incidence of symptomatic hand, hip, and knee osteoarthritis among patients in a health maintainence organization. Arthritis Rheum. 1995;38:1134-1141.

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