Collagen-PVP vs Hylan G-F 20 in the Treatment of Knee Osteoarthritis

Inclusion Criteria: * Aged between 40 and 80 years old * Osteoarthritis in the knee rated II or III (Kellgren-Lawrence Grading Scale). * Pain intensity (MOS Pain Severity Scale) greater than 40. * Subject able to understand, co-operative and reliable. * Written informed consent. Exclusion Criteria: * Acute arthritis in the knee. * Ongoing anticoagulant therapy. * Skin infection at the injection site. * Systemic or intraarticular (target knee) corticosteroids in the past 3 months. * Viscosupplementation (target knee) in the past year * Arthroscopy/osteotomy/surgery in the past 5 months (target knee). * Any surgery scheduled in the next 6 months * Concomitant rheumatic disease (rheumatoid arthritis, spondyloarthritis, systemic lupus erythematosus, fibromyalgia). * Severe varus/valgus deformity (\>15°). * Frontal deformity greater than 20 degrees * History of allergy or hypersensitivity to hyaluronic acid or avian proteins * History/present evidence of: metabolic joint diseases; crystal arthropaties; ochronosis; acromegaly; haemochromatosis; Wilson's disease; primary osteochondromatosis; heritable disorders.