Habitual floor activities increase risk of knee osteoarthritis.

Knee osteoarthritis is a major worldwide public health problem. Mechanical factors generally are considered important in its pathogenesis. Whether floor activities increase the risk of knee osteoarthritis is unclear. We performed a population-based survey to document the association of floor activities with pattern and severity of knee osteoarthritis. We identified 288 women and 288 men 40 years or older from Songkhla province in southern Thailand. We recorded their lifetime histories of four common positions in floor activities: squatting, lotus, side-knee bending, and kneeling. Involvement of osteoarthritis was categorized in three patterns: isolated patellofemoral, isolated tibiofemoral, and combined. We used multinomial logistic regression analysis adjusted for age, gender, body mass index, and smoking status to identify associations between lifetime floor activity and knee osteo-arthritis. Squatting and side-knee bending positions increased the relative risk of radiographic knee osteoarthritis. All types of floor activities except kneeling increased the risk of moderate to severe radiographic knee osteoarthritis. Squatting and lotus positions increased the relative risk of knee pain with radiographic osteoarthritis. Our data suggest habitual lifetime squatting, lotus, and side-knee bending positions increase the risk of knee osteoarthritis.