Effectiveness and Safety of Synvisc® Versus Usual Treatments in Patients With Knee Osteoarthritis

Inclusion Criteria: * Male or female outpatient aged at least 18 years * Patient suffering from predominant femoro-tibial knee osteoarthrosis with or without effusion. The diagnosis must be based on American College of Rheumatology (ACR) criteria. Radiological grade will be assess according to Kellgren-Lawrence scale * Assessment of pain on active movement (i.e. walking) (by the patient) must be at least 40 mm on a 100 mm VAS * Patient who received at least two courses of at least ten days within the last three months with non-steroidal antiinflammatory drugs (NSAID) and/or who are treated continuously for the last two month with slow-acting anti-osteoarthritis drugs * Patient's informed written consent obtained in accordance with French legislation Exclusion Criteria: * Patient suffering from acute congestive osteoarthritis flare of the target knee (at the time of inclusion) which means that concomitantly to knee effusion at least 2 of the following criteria are present: * nocturnal disturbances due to knee pain * morning stiffness over 45 minutes * increase of knee pain more than 50% within the last week * articular reddening * articular heat * Intra-articular administration of hyaluronic acid in the target knee within the previous year * Intra-articular administration of hyaluronic acid in the target knee within the three previous months * Any other intra-articular injection in the target knee within the last 6 months * Any contraindication to intra-articular injections * Present or past history of infected target knee joint * Previous prosthesis knee surgery, tibial osteotomy, synovectomy or synoviorthese of the target knee * Arthroscopy, articular lavage, debridement, menisectomy of the target knee within the previous year * Planned knee surgery within the nine following month * Any other musculoskeletal disorders that can interfere with osteoarthritis diagnosis or the evaluation of its severity * Known hypersensitivity to avian products * Presence of lymphatic or venous stasis * Pregnancy or breastfeeding * Clinical evidence of or known severe cardiac, hepatic, renal, metabolic, haematological disease, mental disturbance * Participation in another clinical trial during this study or during the previous month * Previous participation in this trial * Patient who requires help concerning shopping or house keeping * Patient unable to comply with the protocol (e.g. patient unable to attend each trial visit or to fill the diary booklet or the quality of life questionnaire)