For Peer Review Only Squatting, sitting on the floor, or cycling: are life-long daily activities risk factors for clinical knee osteoarthritis?

Abstract: Objective: To evaluate the association between occupation, sport, life-long daily activities, and knee osteoarthritis. Method: We randomly recruited 480 subjects with knee osteoarthritis who had participated in an earlier community-based study (Tehran-COPCORD, stage-I); they were compared with 490 controls (case-control study). A questionnaire was used to record all occupations/sports, plus details of the following daily activities: standing, walking on flat ground, walking up/downhill, sitting on the floor, sitting on a chair, squatting, knee-bending, cycling, climbing stairs, and carrying loads. The mean time/day spent on these activities was calculated and compared, using the lightest activity as reference. Generalized estimation equation was used, with each knee the unit of analysis. Results: Mean age and female distribution were 57±12, 69.8% for cases, and 46.8±15, 64.1% for controls. Adjusted for age, sex and BMI, two activities were risk factors for knee osteoarthritis: prolonged squatting [OR;1.51,95%CI(1.12-2.04)], and cycling [OR;2.06,95%CI:(1.23-3.45)]. Knee-bending was borderline significant [OR;1.98;95%CI(0.98-3.99)]. Carrying loads [OR;1.24,95%CI(0.87 – 1.76)], or climbing stairs [OR;0.99;95%CI(0.69-1.42)] showed no extra risk factor for knee osteoarthritis. Prolonged standing, sitting on the floor, and walking up/downhill were not risks for knee osteoarthritis. Housewives were at greater risk of developing knee osteoarthritis, [OR;1.68,95%CI(0.93-3.03)](borderline significant) than women whose main occupation was outside home. Other type of jobs/sport did not show extra risk of knee osteoarthritis. Conclusion: Our findings support the role of lifestyle in the pathogenesis of knee osteoarthritis for squatting and cycling. Education on preventable risk factors should be considered in order to ensure people use the knee joints appropriately and avoid overuse.