Helping Osteoarthritis Patients to Walk With NSAID

Inclusion Criteria: * Uni- or bilateral hip or knee idiopathic osteoarthrosis (ACR criteria, Kellgren-Lawrence grade 2 or more on recent X-ray), responsible for pain since 3 at least months, and pain at walking which intensity is at least 4/10 on a numerical rating scale. * Less than 3 relevant walks (at least 20 minutes or 1000 km) a week. * Ability to understand and to follow the protocol, and to answer the questionnaires Exclusion Criteria: * Pregnancy or breastfeeding * Legal protection * Body weight \< 40 kg or underweight * Body weight \>120 kg or obesity * Unability to walk, or unability to walk without support devices (sticks, crutches, orthoses and knee pads are allowed) * Secondary osteoarthrosis (rheumatism, septic arthritis, recent osteonecrosis, hemochromatosis, gout, acromegalia…). * Concomitant general bone disease (Paget, Reiter…). * Concomitant and relevant painful disease else than due to osteoarthrosis (e.g. neuropathic pain, fibromyalgia…) * Previous recent intervention (e.g. surgery, arthroscopy, joint infiltration) expected to relief osteoarthrosis pain throughout the study period. * Planned intervention similar to those abovementioned, during the study period. * Recent initiation of any new analgesic treatment (including systemic steroids). * Planned initiation of any program expected to relief osteoarthrosis pain during the study period, such as physiotherapy, cognitive behavioral therapy…). * Planned major surgery during the study period. * Current cancer disease. * Immunosuppression. * Autoimmune disease. * Concomitant topical or systemic NSAID treatment. * Chronic strong opioid intake. * Concomitant insulin therapy. * Any absolute or relevant contraindication to NSAIDs or acetaminophen, according to the French drug agency