Knee pain and its associations with age, sex, obesity, occupation and living conditions in rural inhabitants of Japan.

Factors associated with knee pain were investigated using 871 self-administered questionnaires (405 men and 466 women) from residents aged over 30 years in a rural area of Japan. The prevalence of knee pain increased with age, particularly in women over 50. It was significantly higher in women than in men. Body mass index (BMI) was significantly related to knee pain in women, though not in men. With reference to occupational factors, frequent heavy lifting on the job was significantly associated with knee pain in both men and women, whereas job-related standing and walking showed no such relationship. As for living conditions, residence on rather steep mountain slopes and the habit of sitting on Japanese tatami mats were significant factors related to knee pain in men, but not in women. There was no association of knee pain with the style of toilet (Japanese or Western). After controlling for all significant factors by multiple logistic regression analysis, age, heavy lifting, and residence on steep slopes were found to be independent factors related to knee pain in men; and age, BMI, and heavy lifting were the factors in women.