Inclusion Criteria:

• Osteoarthritis grade 2-3 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°).
• Knee pain level of at least 5 on the 0-10-point WOMAC A subscale.
• Bilateral osteoarthritis provided that the contralateral knee has a pain no more than 3 on the 0-10 point scale, and not requiring systemic analgesic treatment except paracetamol until the maximum dose of 4g per day.

Exclusion Criteria:

• Grade < 2 or > 3 OA according to the Kellgren and Lawrence grading scale.
• Bilateral osteoarthritis provided that the contralateral knee has a pain more than 3 on the 0-10 point scale and requiring systemic analgesic treatment or paracetamol more than 4g per day.
• Viscosupplementation in the treatment site in the past 3 months.
• Corticosteroid injection in the treatment site in the previous 3 months.
• Systematic use of corticosteroid (except those that are inhaled) within 3 months.
• History of allergy to hyaluronic acid.
• Rheumatological disorders.
• Clinical evidence of local inflammation such as redness or heat of the joint.
• Current or medical history of autoimmune disease.
• Surgery or arthroscopy surgery in the affected knee in the past 3 months.
• Local infection in the affected knee -Hematologic or clotting disorders (thrombocytopenia) or blood coagulation (deficit-blood dyscrasia).
• Anaemia (Haemoglobin < 10g/dl).
• Platelet count below 150/mmc.
• Anticoagulant treatment.
• Viral disease (hepatitis, herpes, varicella, zona, etc.).
• Renal failure or hemodialysis.
• Acute infection.
• Immunosuppressive states.
• Malignant disease.
• Recent fever (within previous 2 weeks) or serious disorders (liver disease, active gastroduodenal ulcer, digestive hemorrhage, etc.).
• Pregnancy or breastfeeding or planning pregnancy during the course of the study.
• Immunosuppressants within the past 6 weeks or ongoing.
• Uncontrolled diabetes.
• Participation in another clinical study in the past 3 months.
• Ongoing participation in another OA clinical study.
• Fracture, skeletal dysplasia, congenital or acquired deformity that affects the knee.
• Hemoglobin A1C > 8% within 8 weeks prior to the study treatment.
• Have been given the diagnosis of fibromyalagia, neuropathic pain syndrome, or depression.
• Refusal to sign or inability to give Informed Consent.
• Inability to understand or comply with the requirements of the study.

Any other reason which may interfere with the proper conduct of the study, in the investigator's opinion.