Efficacy and Safety of 3 Different Dosage Regimens of Hyaluronic Acid in Patients With Knee Osteoarthritis (OA)

Inclusion Criteria: * Outpatient\>45 years of age diagnosed with primary osteoarthritis according to ACR and Kellgren criteria * Knee pain ≥ 55 mm and ≤90 mm measured by Visual Analogue Scale (VAS) 100 mm * Ability to understand and follow study procedures * Written informed consent Exclusion Criteria: * Patients with secondary osteoarthritis of the knee according to ACR criteria. * Severe inflammation of the knee diagnosed by physical examination or a sedimentation speed rate \< 40 mm/h and serum rheumatoid factor titre \< 1:40 * Patients having previously received surgery, including arthroscopy * Patients with joint inflammatory disease (spondilitis, systemic rheumatoid arthritis), microcrystalline arthropathies (chondrocalcinosis, gout, fibromyalgia) and significant osteoarthritis symptoms in other joints apart from the knee, and which require pharmacological treatment * Previous administration of any of the following treatments: hyaluronic acid ia (last year); steroids i.a. or joint lavage (last 3 months), glucosamine sulfate, chondroitin sulfate or diacerein (last 3 months), NSAIDs (last 14 days), any investigational drug (last month) or its administration during this study