To investigate the status of primary osteoarthritis in the population aged 40 years and over in China.

Six centers were selected from China which are Shijiazhuang, Harbin, Shanghai, Guangzhou, Chengdu and Xi'an. The objective population of study included general population of Han nationality aged 40 years and over. In every center, 1 000 people were sampled according to the principles of hierarchy, multistage and cluster random sampling; and the urban and rural areas as well as male and female accounted for half ratio respectively. For the diagnostic criteria of primary osteoarthritis, the diagnostic criteria which were revised by American Society of Rheumatism in 1995 was applied. All joints of knee, hand, cervical and lumbar spine were included.

Under the uniformed inclusion criteria and quantitative index, 6 218 questionnaires and 5 334 sample X-ray films were valid. The prevalence rate of primary osteoarthritis was 46.3% (2 877/6 218), 41.6% (1 212/2 916) in male population and 50.4% (1 665/3 302) in female population. In four different age stages, the prevalence rate of 40-49 years was 30.1% (646/2 145), 50-59 years 48.7% (1 086/2 230), 60-69 years 62.2% (754/1 213) and 70 years and over was 62.1% (391/630). The prevalence of OA in urban and rural areas was 45.6% (1 472/3 225) and 46.9% (1 405/2 993) respectively. The prevalence of OA in cervical spine was 23.6% (1 468/6 218), lumbar spine 29.4% (1 829/6 218), bilateral knee joints 15.6% (972/6 218) and hand joints 7.8% (484/6 218).

Based on the investigation of six administrative regions in China, the total prevalence rate of primary osteoarthritis was 46.3% and there was an increasing trend with aging. The prevalence rate of female population was higher than that of male population and there was no statistical difference between urban and rural population.

Osteoarthritis; Prevalence; Epidemiologic studies; China