Articular cartilage degradation is the main characteristic of osteoarthritis (OA), involving enzymatic and inflammatory mechanisms that change it into a chronic disease. Since articular cartilage shows limited regenerative ability, several intra-articular drugs have been developed in order to decrease inflammation and provide a better clinical outcome to the patient.

This study aims to compare effectiveness of the treatment with intra-articular administration of collagen-PVP versus hylan GF 20, using the International Knee Documentation Committee (IKDC) score, 6 months after treatment. Hypothesis to test is: If effectiveness of intra-articular collagen-PVP is not lower than hylan GF 20 treatment in knee osteoarthritis subjects, then, statistically significant difference would not exist in IKDC score mean increase among treatment groups, after six months.

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.

Double-blind masking.