ABSTRACTObjective Find out whether daily physical activities of Islamic praying predispose to or protect from osteoarthritis (OA) of weight bearing joints. Methods Comparison of prevalence of primary OA of knees and/or hips between age and weight matched prayers and non-prayers men. Civil official and employees from different establishments in Erbil City (191 Subjects) and (21 Subjects) from out-patient clinics of Rizgary and Erbil Teaching Hospital-Erbil, over a period of eight months starting on Jan.2004. This constituted one hundred and eleven prayers and 101 subjects not practicing Islamic praying. Subjects fulfilling our inclusion criteria underwent clinical evaluation and radiology of their knee and hip joints. We assessed, by Chi-squared test, differences in frequency of OA between prayers and non-prayers, and between the > 20 year prayers who lay hands first on prostrating from erect posture and the same duration prayers who lay their knees first. Results No single OA of hip was encountered. OA of knees was significantly less (p. < 0.01) prevalent among prayers than those who did not practice Islamic praying.differentially, Laying knees first on prostrating from erect posture was associated with significantly (p. <0.05) higher frequency of OA of knees as compared with those who lay their hands first on the praying rug(ground). Conclusion Islamic praying in 46-60 year-old men, of normal or marginal overweight (BMI 20-27kg/m2), protects from primary OA of the knees. Laying palms first on prostrating from standing position appears to preclude a likely harmful effect on the knee joints presumably from repeated "hitting" of ground under the praying rug if laid first on prostration.