Eighteen studies on prevalence and one study on incidence met the inclusion criteria. Incidence figures of 0.9-2.5% were found for different age groups. Prevalence figures differed from 6.9 to 26% for point prevalence, 18.6-31%, for 1-month prevalence, 4.7-46.7% for 1-year prevalence and 6.7-66.7% for lifetime prevalence. Prevalence rates decreased when the case definition was restricted, in terms of duration of pain or the presence of limited movements, and increased when the location for pain was enlarged.