Innovative Tool to Analyse Synovial Fluid of Patients With Knee Ostearthritis After IA Injection of Synvisc-one®

Inclusion Criteria: * Male or female ≥ 40 years of age with BMI ≤ 35 kg/m2 * Femorotibial knee OA (Uni- or bilateral): * Responding to clinical and radiological criteria of American College of Rheumatology (ACR) * Symptomatic for more than 6 months in the most painful knee * Moderate-to-severe knee pain: knee pain score evaluated on VAS (0-100) ≥ 40 over the last month at the inclusion visit (the most painful knee is considered) * Eligible for knee viscosupplementation using SYNVISC-ONE® * Knee swelling justifying SF aspiration at baseline - Able to follow the instructions of the study * Having signed an informed consent Exclusion Criteria: 1. Related to the OA pathology * Recent macro-trauma (\< 6 months) of the knee responsible of the symptomatic knee. Micro-trauma are allowed according the Investigator's discretion * Concurrent articular disease interfering with the evaluation of OA and/or pain such as but not limited to articular dysplasia, aseptic osteonecrosis, acromegaly, Paget's disease, hemophilia, hemochromatosis, chondromatosis, villonodular synovitis of the knee, seronegative spondyloarthropathy, rheumatoid arthritis, gouty arthritis, infectious arthritis, radiculalgia in the lower limbs, arteritis, chondrocalcinosis x-rays diagnosed and Calcium PyroPhosphate Dihydrate crystal deposition disease (CPPD) * Hemarthrosis * Prosthesis in the target knee 2. Related to treatment * Corticosteroids injection in the target knee in the last 3 months before injection (excepted for low dose injection following SF aspiration at V1 as recommended by standard treatment guidelines) * Hyaluronan injection in the target knee in the last 6 months before injection * Arthroscopy in the last 3 months before injection * Oral corticotherapy ≥ 5mg/day (in Prednisolone equivalent) in the last 3 months before injection * Change in the dosage regimen of symptomatic slow-acting drugs for osteoarthritis (SYSADOA) or dietary supplement, i.e., curcuma extract, chondroitin, glucosamine, diacerein or avocado-soya unsaponifiables in the last 3 months before injection * An anticipated need for any forbidden OA treatments during the trial * Contraindications to SYNVISC-ONE®: hypersensitivity or allergy to the product components and infections or skin diseases in the area of the injection site * Anticoagulant anti-vitamin K (such as coumarinic) before injection 3. Related to associated diseases * Severe and uncontrolled diseases (type I diabetes, liver failure, renal failure, lung/heart disease, progressive malignant neoplasia or in remission for less than 5 years, HIV) * Malignancy or history of malignancy, or other major disease (e.g., systemic fungal infection) or other severe uncontrolled conditions (e.g., drug or alcohol abuse), that are significant and/or that may pose a health risk to the subject in the study or may have an impact on the study assessments * High risk of hemorrhage and risk of infection at the site of injection * Anticipated need for any surgical or other invasive procedure during the trial including prosthesis in the target knee 4. Related to patients * Close collaborators to the Sponsor, the study coordinator or the Investigator * Participation in a clinical trial in the last 3 months before injection * Patient under guardianship or judicial protection * Pregnancy, breastfeeding, planned conception, or premenopausal women without effective contraception (pill, patch, ring, diaphragm, implant and intrauterine device), tubal ligation or hysterectomy 5. Related to MRI counter-indication * Risk groups for MRI scanning due to magnetic field: metal in body: pacemaker/AICD/ICD (coronary defibrillator), nervus vagus stimulator, artificial heart valve (depending on type), metal clips on cerebral arteries or veins, metal particles in eye, port-a-cath, metal stents, hydrocephalic pump/insuline pump, metal implants; f/e screws, prostheses, piercings * Claustrophobia or serious mobility problem (uncontrolled Parkinson, tremors)