Epidemiology of Osteoarthritis
Section snippets
Defining osteoarthritis
Epidemiologic principles can be used to describe the distribution of OA in the population and to examine risk factors for its occurrence and progression. For the purpose of epidemiologic investigation, OA can be defined pathologically, radiographically, or clinically. Radiographic OA has long been considered the reference standard, and multiple ways to define radiographic disease have been devised. The most common method for radiographic definition is the Kellgren-Lawrence (K/L) radiographic
Prevalence and incidence of osteoarthritis
The prevalence of OA varies according to the definition of OA, the specific joint(s) under study, and the characteristics of the study population. The age-standardized prevalence of radiographic knee OA in adults age 45 years or older was 19.2% among the participants in the Framingham Study and 27.8% in the Johnston County Osteoarthritis Project.6 In the third National Health and Nutrition Examination Survey (NHANES III), approximately 37% of participants older than 60 years had radiographic
Risk factors for osteoarthritis
OA has a multifactorial etiology, and can be considered the product of an interplay between systemic and local factors as shown in Fig. 2.1 For example, a person may have an inherited predisposition to develop OA but may only develop it if an insult to the joint has occurred. The relative importance of risk factors may vary for different joints, for different stages of the disease, for the development as opposed to the progression of disease, and for radiographic versus symptomatic disease.
Age
Age is a one of the strongest risk factors for OA of all joints.1, 6, 15 The increase in the prevalence and incidence of OA with age probably is a consequence of cumulative exposure to various risk factors and biologic changes that occur with aging that may make a joint less able to cope with adversity, such as cartilage thinning, weak muscle strength, poor proprioception, and oxidative damage.
Gender and Hormones
Women not only are more likely to have OA than men, they also have more severe OA.16 The definite
Obesity
Obesity and overweight have long been recognized as potent risk factors for OA, especially OA of the knee.1 The results from the Framingham Study demonstrated that women who had lost about 5 kg had a 50% reduction in the risk of development of symptomatic knee OA.55 The same study also found that weight loss was strongly associated with a reduced risk of development of radiographic knee OA. Weight-loss interventions have been shown to decrease pain and disability in established knee OA.56, 57
Occupation
Repetitive use of joints at work is associated with an increased risk of OA. Studies have found that farmers have a high prevalence of hip OA.65 The prevalence of Heberden nodes was much higher in cotton mill workers, whereas spinal OA was no more common in these workers than in controls.66 Workers whose jobs required repeated pincer grip had more OA at distal interphalangeal joints than did workers whose job required power grip.67
The risk of development of knee OA was more than 2 times greater
Risk factors for symptomatic osteoarthritis
Although symptomatic knee OA is common, causes substantial disability, and consumes tremendous medical costs, most previous studies have focused on risk factors for radiographic OA.1 Not all risk factors for radiographic OA are strong predictors of joint symptoms.1, 15 Women with radiographic knee OA were more likely to have symptoms than men,95 and African Americans generally reported more knee and hip symptoms than whites.96 Strenuous physical activity, especially activities requiring
Summary
Evolving definitions of OA and improvement in risk factor measurement, by using advanced imaging, systemic and local biomarkers, and improved methods for measuring symptoms and their impact, can help to elucidate mechanisms and identify potential areas for intervention or prevention. The application of these new sources of knowledge about the OA process holds promise for the development of new, potentially disease-modifying pharmaceuticals and nonpharmacologic therapies.
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