To assess the impact of the distinct diagnostic criteria used in population-based studies on estimation of the prevalence of knee osteoarthritis.
We performed a search for population-based studies of the prevalence of knee osteoarthritis carried out in the general noninstitutionalized population in Europe or the USA.
Eight articles were selected, six from Europe and two from the USA. Depending on the study, definition of knee osteoarthritis was based on symptomatic criteria (pain), radiological criteria (the Kellgren and Lawrence scale) or a combination of both symptomatic and radiological criteria. Prevalence estimates ranged from 2.0 to 42.4% with symptomatic criteria, from 16.3 to 33.0% with radiological criteria, and from 1.5 to 15.9% when both criteria were combined. The prevalence was higher for women and increased with age, with the exception of some prevalences estimated through symptoms, which decreased in ages older than 80 years.
There is a lack of consensus on the criteria used to diagnose knee osteoarthritis in population-based studies of prevalence. Consequently, prevalence estimates vary widely, depending on the diagnostic criteria used, and not only by age and sex. The prevalence was higher when radiological evidence alone was used, followed by symptomatic criteria and by combinations of both.