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CME

Prevalence of Knee Pain Increased During 20 Years

  • Authors: News Author: Steven Fox
    CME Author: Désirée Lie, MD, MSEd
  • CME Released: 12/20/2011
  • THIS ACTIVITY HAS EXPIRED
  • Valid for credit through: 12/20/2012
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Target Audience and Goal Statement

This article is intended for primary care clinicians, orthopaedists, radiologists, and other specialists who care for patients with knee pain.

The goal of this activity is to provide medical news to primary care clinicians and other healthcare professionals in order to enhance patient care.

Upon completion of this activity, participants will be able to:

  1. Describe the prevalence of knee pain during the last 20 years.
  2. Describe the prevalence of symptomatic knee osteoarthritis during the last 20 years.


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Author(s)

  • Steven Fox

    Steven Fox is a freelancer for Medscape.

    Disclosures

    Disclosure: Steven Fox has disclosed no relevant financial information.

Editor(s)

  • Brande Nicole Martin, MA

    CME Clinical Editor, Medscape, LLC

    Disclosures

    Disclosure: Brande Nicole Martin, MA, has disclosed no relevant financial relationships.

CME Author(s)

  • Désirée Lie, MD, MSEd

    Clinical Professor; Director of Research and Faculty Development, Department of Family Medicine, University of California, Irvine at Orange

    Disclosures

    Disclosure: Désirée Lie, MD, MSEd, has disclosed the following relevant financial relationship:
    Served as a nonproduct speaker for: "Topics in Health" for Merck Speaker Services

CME Reviewer(s)

  • Sarah Fleischman

    CME Program Manager, Medscape, LLC

    Disclosures

    Disclosure: Sarah Fleischman has disclosed no relevant financial relationships.


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CME

Prevalence of Knee Pain Increased During 20 Years

Authors: News Author: Steven Fox CME Author: Désirée Lie, MD, MSEdFaculty and Disclosures
THIS ACTIVITY HAS EXPIRED

CME Released: 12/20/2011

Valid for credit through: 12/20/2012

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Clinical Context

According to the current study by Nguyen and colleagues, frequent knee pain affects 25% of adults, and osteoarthritis is the most common cause of knee pain in adults 50 years and older. In recent years, the rate of knee replacements has surged. Rates have tripled in women in the United Kingdom and have increased 8 times in the United States among those 65 years and older.

This study of data from the National Health and Nutrition Examination Surveys (NHANES) and the Framingham Osteoarthritis (FOA) cohorts examines the changing prevalence of knee pain and knee osteoarthritis as time progresses.

Study Synopsis and Perspective

The prevalence of knee pain and knee replacement surgeries has risen substantially during the last 20 years. However, the reasons for the increase remain obscure, according to a study published in the December issue of the Annals of Internal Medicine.

"A recent surge in knee replacements is assumed to be due to aging and increased obesity of the U.S. population," write Uyen-Sa D.T. Nguyen, DSc, Clinical Epidemiology Research & Training Unit, Boston University School of Medicine, and Brigham and Women’s Hospital, Boston, Massachusetts, and colleagues. However, the team's analysis suggest the rise in knee surgeries may be linked more to increasing knee pain or an increased awareness of knee pain.

"Using data from 2 community-based studies, we found that the age- and [body mass index (BMI)-]adjusted prevalence of knee pain over 20 years has increased for non-Hispanic white and Mexican American men and women and African American women," the authors write. "Adjustment for age did not substantially alter the prevalence estimate for knee pain or symptomatic knee osteoarthritis over time, whereas additional adjustment for BMI resulted in a 10% to 25% decrease in prevalence ratios."

To understand what is driving the increase in total knee replacements, Dr. Nguyen and colleagues evaluated results from 6 NHANES studies conducted between 1971 and 2004, and from 3 examination periods in the FOA Study carried out between 1983 and 2005.

"We examined whether a change in the prevalence of knee pain and symptomatic knee osteoarthritis could be attributed to age, [BMI], or radiographic knee osteoarthritis," the researchers write.

Participants in the NHANES surveys were white or black and were aged 60 to 74 years. More than 6900 people were included in that study. Participants in the FOA Study were predominately white and at least 70 years old. The number of people evaluated in the FOA Study were 902, 1132, and 671 from the 3 exam periods, respectively.

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 to 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.

"These increases may explain the surge in knee replacement surgeries and suggest a bigger burden of knee pain in our society than previously thought," they write.

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 (P for trend = 0.82) and actually may have decreased for women (P for trend = 0.036)," the authors write.

They conclude that even though the prevalence of knee pain, independent of increasing age and rates of obesity, has risen during the last 20 years, obesity accounted for only part of the increase.

In an accompanying editorial, Allan Gelber, MD, MPH, PhD, from Johns Hopkins University School of Medicine in Baltimore, Maryland, comments, "These findings call both the health services researcher and the treating clinician alike to action."

He adds, "This reality compels the treating physician to 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."

The study was supported by the National Institutes of Health and an American College of Rheumatology Research and Education Foundation Rheumatology Scientist Development Award. The Framingham Heart Study was funded by the National Heart, Lung, and Blood Institute, and the FOA Study was funded by the National Institute on Aging and National Institute of Arthritis and Musculoskeletal and Skin Diseases. The authors and Dr. Gelber have disclosed no relevant financial relationships.

Ann Intern Med. 2011;155:725-732. Article abstract, Editorial

Study Highlights

  • The data were obtained from the NHANES and the FOA Study.
  • Cross-sectional surveys from the NHANES studies were used for participants 60 to 74 years old and included white, Mexican American, and African American participants.
  • The FAO study included participants from the Original Framingham cohort, the Offspring cohort, and a Community cohort.
  • The osteoarthritis assessment was conducted at several intervals for both sets of cohorts.
  • Data on knee pain were collected at intervals for the NHANES and the Framingham cohorts, asking about pain in or around the knee on most days or for at least 1 month in the previous 12 months.
  • Weight-bearing posteroanterior radiographic study was performed for the Community cohort and both posteroanterior and anteroposterior radiographic study performed for the Offspring cohort of the FOA Study.
  • Radiographic features were assessed with use of the Kellgren-Lawrence scale of 0 to 4 based on the presence of osteophytes, joint space narrowing, sclerosis, attrition, and cysts.
  • Knee osteoarthritis was considered to be present if the Kellgren-Lawrence score was 2 or higher.
  • The prevalence of knee pain and symptomatic knee osteoarthritis was estimated after adjustment for age and BMI.
  • In the first 3 NHANES surveys, there were 1382, 4342, and 3682 participants, respectively.
  • For the subsequent 3 NHANES surveys, there were 1066, 1011, and 1054 participants, respectively.
  • For the FOA Study, there were 902, 1132, and 671 participants during 3 intervals.
  • The prevalence of knee pain increased in both the NHANES and the FOA cohorts with time.
  • The age- and BMI- adjusted prevalence of knee pain increased by 66% in NHANES from 1974 to 1994, with significant trends for white men (P for trend = .003) and white women (P for trend = .002).
  • The trend increased further from 1999 to 2004 in white women but was borderline significant for white men in the NHANES study.
  • In the FOA Study, the prevalence of knee pain doubled during 20 years for women and tripled for men.
  • In participants without radiographic knee osteoarthritis, the prevalence of knee pain tripled in women and quadrupled in men during the last 20 years.
  • Among those from the FOA Study with radiographic knee osteoarthritis, the prevalence estimates were 26.3%, 31.1%, and 48.5% in women at 3 different intervals and 19.0%, 21.7%, and 49.4% in men (P for trend < .001).
  • After adjustment for age and BMI, the prevalence of knee osteoarthritis in the FOA Study tripled in men and almost doubled in women in the last 20 years.
  • However, the age- and BMI-adjusted prevalence of radiographic knee osteoarthritis did not change during this period for men and may have decreased for women.
  • The authors concluded that knee pain has increased with time for men and women and that symptomatic knee osteoarthritis also increased, but radiographic knee osteoarthritis did not.

Clinical Implications

  • The prevalence of knee pain has increased during the last 20 years, independent of age and BMI.
  • The prevalence of symptomatic knee osteoarthritis has increased during the last 20 years, but the prevalence of radiographic knee osteoarthritis has not.

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