Clinical trial with medical device, multicenter, single-blind (blind third party evaluation), randomized, comparative and in two paralell groups, to demonstrate the treatment according to usual clinical practice, of the combination of 50 mg Sodium Hyaluronate and 50 mg Chondroitin Sulfate (ENKO 1) in a single administration, has non-inferiority efficacy vs the comparator (Durolane; 60 mg HA crosslinked) in patients with symptomatic knee osteoarthritis after three months of follow-up.

Inclusion Criteria:

• Medial femorotibial compartment knee OA.
• Fulfilment of ACR criteria for knee OA (knee pain + grinding + stiffness in the morning < 30 minutes).
• Patients with a clinical course of disease longer than 6 months.
• Global pain score greater than 60 mm on a 0-100 mm VAS on the knee under study.
• Grade II or III according to the Kellgren and Lawrence classification system for the knee under study (on a posteroanterior X-ray performed under weight-bearing and for 6 months before randomisation).
• Patients taking analgesics for at least 3 months before randomisation and whom are dissatisfied with their current therapy.
• Patients who have given their consent in writing to take part in the study.
• Woman of childbearing age must take a urine pregnancy test which must be negative at the randomisation visit and be currently using an effective contraceptive method for at least 2 menstrual cycles (oral contraceptives, intrauterine device, tubal ligation or other effective procedures).

Exclusion Criteria:

• Isolated symptomatic patellofemoral osteoarthritis.
• Microcrystalline osteoarthritis.
• Prosthesis in knee under study.
• Joint lavage or arthroscopy or any surgery on the knee under study in the 6 months before randomisation.
• Paget's disease of bone, chondromatosis or villonodular sinovitis.
• Inflammatory, infectious or metabolic arthritis (rheumatoid arthritis, spondyloarthropathy or connective tissue diseases).
• Haemochromatosis, ochronosis or haemophilia.
• History of diseases that the investigator considers likely to interfere with the functional disability assessment.
• Knee surgery planned during the study period.

Other disease-related criteria:

• BMI greater than or equal to 30.
• Immunodeficiency or a serious or progressive disease (heart, lung, liver, kidney, haematological, neoplastic or infectious disease).
• Skin diseases or infections in the area of the injection site.
• Previous history of venous thromboembolism (including pulmonary embolism) or high risk of venous thromboembolism.
• Venous or lymphatic stasis of the leg under study.
• Severe acute or chronic disease that the investigator considers incompatible with the conduct of the study.
• Disease that the investigator considers likely to interfere with the study results or to expose the patient to an additional risk.
• Alcohol or drug abuse or dependence.

Previous or concomitant treatment-related criteria:

• Patients who have taken a SYSADOA, SERM or a drug/dietary supplement containing glucosamine, chondroitin sulfate, diacerein or avocado-soybean extracts in the 3 months before randomisation
• Patients who have taken paracetamol in the 24 hours before randomisation or any other symptomatic analgesic drug, including NSAIDs (except aspirin up to 325 mg/day for cardiovascular prophylaxis), in the 48 hours before randomisation
• Patients who have received any corticosteroid treatment by any route of administration (other than inhalers or the ocular or auricular routes) in the month before randomisation
• Patients who have received an intra-articular steroid injection in the knee under study in the month before randomisation or patients who have received intra-articular hyaluronic acid in the target knee in the 6 months before randomisation
• Patients who have received any local or topical treatment on the target knee in the 2 weeks before randomisation

Criteria related to concomitant medication:

• Hypersensitivity to paracetamol or NSAIDs

Study product-related criteria:

• Known allergy to the study treatments or to any of its ingredients.

Other criteria:

• Patients likely to be unable to comply with the protocol instructions and/or treatment, in the investigator's opinion
• Patients who have taken part in a clinical trial in the preceding 2 months or taking part in a trial at the time of randomisation
• Patients linguistically or mentally incapable of understanding the nature, objectives and possible consequences of the study; or who refuse to be subject to its limitations
• Patients who are family or colleagues (secretary, nurse, technician, etc.) of the investigator.
• Women: pregnant or breastfeeding

Single-blinded (blind third party evaluation) The physician performing the infiltration will be different and cannot be related to the investigator evaluating the results.