Combination of PRP and XLHA Prepared With RegenMatrix Medical Device To Treat Moderate to Severe Knee Osteoarthritis

Inclusion Criteria: * Tibiofemoral knee osteoarthrosis according to ACR criteria * Tibiofemoral knee osteoarthrosis grade 3-4 according to the Kellgren \& Lawrence grading scale, as defined on knee radiographs (less than 3 months old: face view, schuss view, profile and patellar axial view at 30°) * Symptomatic knee osteoarthrosis as evidenced by pain on walking (WOMAC A1 assessed in the last 24 hours on a scale of 0 to 100 mm: 50 ≤ DM 90 or reduced joint function (WOMAC C total score assessed or within the previous 24 hours based on a scale of 0-100-mm: 50 ≤ WOMAC C ≤ 90) * Patient able to understand the requirements of the trial and who has signed a free and informed consent prior to study entry * Patient able to read and understand the written instructions * Patient able to complete the self-assessment questionnaires Exclusion Criteria: * Tibiofemoral knee osteoarthrosis grade I or II according to the Kellgren and Lawrence grading scale * Knee surgery planned in the next 6 months * Patient affected by autoimmune disease (rheumatoid arthritis, lupus, Hashimoto's disease and Bechterew's syndrome) * Chronic inflammatory rheumatism other than arthritis (polyarthrosis, etc.) * Patient affected by a knee infection in the past 6 months * Clinical signs of local knee inflammation (redness or warmth of the knee joint) * Last PRP or PRP/HA injection received in the last year * Last viscosupplementation received in the past 6 months * Last corticosteroid injection received in the past 3 months * Use of gluco-corticosteroids (except inhaled) and level III analgesics in the last 3 months and non-steroidal anti-inflammatory drug in the last 2 weeks * Treatment with AAAL initiated within the last 6 months * History of allergy to hyaluronic acid * Hematologic or clotting disorders (thrombocytopenia) or blood coagulation (deficit-blood dyscrasia) * Patients with coagulation times outside the reference values * Anemia (HGB\<10 g/dl) * Venous or lymphatic stasis in the corresponding limb * Malignant diseases (especially bone or haematological) * Patients with serious, no-stabilized pathologies (cardiovascular disease, active peptic ulcer, digestive hemorrhage) * Acute infection * Patients with cancer or with an immuno-deprassant treatment ongoing * Participation in another clinical trial for osteoarthritis of the knee in the last year * Participation in another clinical trial, ongoing or completed within the last 3 months * Patient unable to comply with the constraints of the protocol, in particular a patient whose mental state does not allow him/her to patient's mental state does not allow him/her to understand the nature, objectives and possible consequences of the study * Pregnant or breastfeeding women or women who expect to become pregnant during the study * Any other reason which may interfere with the proper conduct of the study, in the investigator's opinion