Trends in prevalence of knee
pain among US adults, National Health Interview Survey, 2002-2010

Background/Purpose : Aging of the population as well as the obesity
epidemic will play a significant role in future cases of arthritis and other
lower extremity orthopedic conditions.  The purpose of this study is to examine
trends in the prevalence of knee pain among adults age 18 and older, overall
and by age and sex.

Methods :  The National Health Interview Survey, conducted
annually, targets the civilian, non-institutionalized population and gathers
data on a variety of health topics.  From 2002 – 2010 the adult sample size
ranged from 21,781 to 31,428. Adults were asked if they had joint pain in the
past 30 days not including the back or neck.  For those responding “yes”,
respondents were then asked what joints were affected. Prevalence (%) and 95%
confidence intervals (CI) of knee pain were calculated using design variables
and sampling weights to account for the complex survey design.  Prevalence was
also stratified by age group (18-24, 25-44, 45-64, 65-74, 75+) and sex, and
graphed by age to show trends over time.  Percent increase was calculated using
the formula: (prevalence 2010 – prevalence 2002)/prevalence 2002*100.
Statistical significance was determined by non-overlapping 95% CIs.

Results : The overall age-adjusted prevalence of knee pain
increased significantly from 16.5% (CI 15.6-17.4) in 2002 to 19.6% (CI
18.5-20.7) in 2010. With a few exceptions, in each year, knee pain prevalence
was higher with increasing age and highest for the 75+ age group. (Figure) For
most years more than 1 in 4 adults aged 55-64 and 65-74 and 75+ reported having
knee painr. Knee pain prevalence increased significantly over the 9 years in
all age groups. The age groups with the largest percent increase were 25-44 (+21.4%),
45-64 (+27.7%), and 55-64 (+25.2%).  Women had higher prevalence of knee pain
than men for all years, but prevalence increased more in men (+23.0%) versus
women (+15.3%).

Conclusion :  Knee pain prevalence is high and has increased over
time for all age groups with adults aged 45-54and 55-64 showing the largest
increases.  The findings suggest a large burden of knee pain among working age
adults.  Public health and worksite wellness efforts should consider
implementing evidence-based interventions aimed at reducing knee pain such as
physical therapy, aerobic and muscle strengthening exercises, and weight loss. The
data also support the need for increasing the number of primary care, rheumatology
and orthopedic health professionals in the workforce to address the growing
burden of knee pain in the population.