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Trends in Knee Pain and Knee Osteoarthritis FREE

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The full report is titled “Increasing Prevalence of Knee Pain and Symptomatic Knee Osteoarthritis: Survey and Cohort Data.” It is in the 6 December 2011 issue of Annals of Internal Medicine (volume 155, pages 725-732). The authors are U.S.D.T. Nguyen, Y. Zhang, Y. Zhu, J. Niu, B. Zhang, and D.T. Felson.

Ann Intern Med. 2011;155(11):I-46. doi:10.7326/0003-4819-155-11-201112060-00001
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What is the problem and what is known about it so far?

Rates of knee replacement surgery more than tripled in the United Kingdom between 1991 and 2006 and increased about 8-fold in the United States between 1979 and 2002. We do not understand why knee replacements are being done more frequently. On the basis of the aging of the population and increased rates of obesity (another major risk factor for knee arthritis), we expect that knee arthritis rates are increasing, but there are no data to support this.

Why did the researchers do this particular study?

To assess the trend in knee pain and symptomatic knee osteoarthritis, which are main reasons for knee replacement surgery.

Who was studied?

Representative samples of the U.S. population who have been surveyed periodically since 1971 in the National Health and Nutrition Examination Survey (NHANES) and participants in the Framingham Heart Study, which is a population-based study that began in 1948.

How was the study done?

Researchers asked participants in the first study about pain in or around the knee on most days for at least 4 to 6 weeks. Researchers asked participants in the second study about pain in or around the knee that lasted at least 1 month during the previous 12 months and took x-rays of both knees.

What did the researchers find?

In the first study, the frequency of knee pain increased about 65% in men and women in the 20 years after 1974, after adjustment for changes in age and weight. In the second study, the frequency of knee pain doubled in women and tripled in men over a 20-year period, after adjustment for changes in age and weight, but x-rays showed no change in the frequency of knee arthritis.

What were the limitations of the study?

In both studies, different people were studied during different periods, so the changing composition of the study groups might explain some of the results; however, this limitation is less relevant to the first study.

What are the implications of the study?

The prevalence of knee pain is increasing without evidence of increasing osteoarthritis, and the increased pain is not explained by increased age or obesity.





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