WebMD Medical News
Louise Chang, MD
Sept. 5, 2008 -- Nearly half of Americans are likely to develop arthritis in at least one knee by
age 85. For people who are obese, the risk is greater.
Researchers from the CDC and the
University of North Carolina studied data on 3,068 people in Johnston County,
N.C. Participants, all 45 years old or older, were evaluated twice over an
average follow-up of six years. Participants received physical exams, X-rays,
and also were interviewed.
Researchers were able to use the data to estimate risk of developing
symptomatic knee osteoarthritis (OA) by their
mid-80s. OA is the most common form of arthritis.
At the start of the study, the average age of participants in the study was
61 with 15% having symptomatic knee OA. About six in 10 of the participants
were overweight or obese. Though the study focused on one small geographic
area, the researchers say the data are likely applicable to Americans as a
Researchers found that the lifetime risk of having symptomatic knee
osteoarthritis was 44.7%. Sex, education level, and race didn't seem to affect
a person's chances of developing arthritis. The two factors that do have an
effect: whether or not someone has a past knee injury and whether or not the
person is overweight or obese.
Participants with a history of knee injury have a 56.8 % risk, compared with
a 42.3 % risk for those without past knee injury. People of normal weight have a risk of
30.2% of developing knee osteoarthritis with symptoms, compared with 46.9% for
overweight participants and 60.5% for obese participants.
The researchers, who write that arthritis is a leading cause of disability
in the U.S., call for more focus on weight management by both
individuals and their doctors.
"Simply put, people who keep their weight within the normal range are
much less likely to develop symptomatic knee osteoarthritis as they get older
and thus much less likely to face the need for major surgical procedures, such
as knee replacement surgery,"
says Joanne Jordan, MD, in a news release. Jordan is principal investigator of
the Johnston County Osteoarthritis Project and a senior study researcher. She
is also a professor of medicine and orthopaedics in the School of Medicine at
the University of North Carolina.
The Johnston County Osteoarthritis Project is funded primarily by the
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SOURCES:Murphy, L. Arthritis & Rheumatism, September 2008; vol 59: pp
1207-1213.News release, University of North Carolina at Chapel Hill School of
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