If all the etiological factors are taken into consideration, idiopathic coxarthrosis is less prevalent than formerly. Three factors are new or reappraised: sport practice (more than 10 years in competition), certain occupations (dancer, heavy load worker) and heritability. Three are classical and yet present: developmental dysplasias, acquired dysmorphias and traumas. Hip osteoarthritis should be followed up with the help of pain intensity measured on visual analog scale, algofunctional index and self-assessment of handicap. These 3 parameters--and not the X-ray image--are the basis of the decision for total hip replacement. However, the latter could be foreseen as necessary within the next 1-4 years when a rapid joint space narrowing is observed (about 5-7% of cases).