Even though the prevalence of knee pain has risen during the last 20 years, obesity and osteoarthritis account for only part of the increase, according to a Medscape Medical News article based on a study published this month in Annals of Internal Medicine.
For this analysis, researchers evaluated results from 6 National Health and Nutrition Examination Surveys (NHANES) conducted between 1971 and 2004, and from 3 exam periods in the Framingham Osteoarthritis (FOA) Study carried out between 1983 and 2005. Participants in both studies were asked whether they experienced knee pain most days. In addition, participants in the FOA study underwent bilateral weight-bearing radiographs of their knees to assess the presence and extent of osteoarthritis. Radiographs were combined with self-reported knee pain to define symptomatic knee osteoarthritis.
The researchers found that from 1974-1994, several ethnic groups in the NHANES study, namely, non-Hispanic white and Mexican-American men and women and black women, experienced a 65% increase in age- and BMI-adjusted knee pain. Among FOA participants, the prevalence of age- and BMI-adjusted knee pain and symptomatic osteoarthritis approximately doubled in 20 years among women, and tripled among men.
Remarkably, the researchers saw no such trend among FOA participants in terms of the prevalence of radiographic evidence of osteoarthritis. "[T]he age- and BMI-adjusted prevalence of radiographic knee osteoarthritis did not substantially change over this same period for men and actually may have decreased for women," the article says.
An accompanying editorial says clinicians should "carefully consider, from the signs and symptoms of the patient presenting with knee pain, a broad differential diagnosis. Not all knee pain in middle-aged and older adults is the result of osteoarthritis."