Ideally, treatment is based on etiology, if possible on pathophysiology, and in practice on anatomical and clinical findings. A systematic search for the etiological factors of osteoarthritis (OA) shows that the various mechanisms are frequently associated. Etiological treatments are rare. We may mention acetabular tectoplasty in hip dysplasia with minimal joint space narrowing. Valgus osteotomy would also be indicated for early medial tibiofemoral OA in genu varum if we had definite proof that, if left untreated, this deformity inevitably leads to clinically severe OA. This is not the case. One of the limitations of this etiological treatment lies in the fact that we do not know which patients are at risk of developing painful OA. Instead, certain risk factors for OA are known, so that primary and secondary prevention of the disease is possible. While age, sex and genetic predisposition are not amenable to preventive action, the same does not apply to the following factors: obesity, sports, and occupational activity. Thanks to in vitro studies of cultured normal and osteoarthritic chondrocytes and to experimental models of OA in animals, the pathophysiological mechanisms of OA are beginning to be better known. The prospect thus arises of "therapeutic manipulations" of precise pharmacological targets, even if it is still too soon to speak of true pathophysiological treatment of this disease. For instance, various interventions along the IL-1 pathway can be envisaged and have all been tested in animals. In practice, treating OA means taking into consideration its various signs: pain which appears to be mechanical and more or less chronic, joint stiffness, instability, effusion, and--the consequence of these symptoms--the professional, social and personal handicap of the patient. The treatment of OA must be approached from a global perspective, associating whenever possible symptomatic treatment, disease-modifying treatment, education and rehabilitation. In other words, the treatment of OA requires an overall approach, associating pharmacological and non-pharmacological modalities.