Assessment of Efficacy of a Single Intra-articular Injection of HYALUBRIX 60 in Knee Osteoarthritis

Inclusion Criteria: 1. Voluntarily given informed consent to investigation participation in writing encompassing consent to data recording and verification procedures; 2. Male or female subjects aged ≥18 years and ≤70 years with active life-style; 3. BMI ≤40 kg/m2; 4. Patients affected by knee osteoarthritis, as defined by American College of Rheumatology (ACR) clinical and radiographic criteria for OA of the knee, and meeting the following conditions: * Kellgren-Lawrence Grade 2 to 3 severity OA of the target knee with presence of osteophytes determined from X-rays of the knee obtained within 6 months from the screening visit; i.e. in the tibio-femoral compartment of the target knee with at least 1 osteophyte and measurable joint space, as diagnosed by standard X-rays (anterior- posterior view \[weight bearing extension or semi-flexion\] and lateral). In the case that a patient has not a valid X-ray within 6 months prior to screening, the exam is to be performed during the screening period; * Patients suffering from OA symptoms of the target knee for at least 3 months prior to the screening visit; Note: patients with bilateral OA of the knee will be allowed as long as they can differentiate pain in the target knee, do not need to use analgesics for treatment of their contralateral knee, and do not expect to receive treatment of the contralateral knee during the investigation. In the case that both knees are eligible for the investigation based on pain intensity, the knee with the greater pain VAS score on the WOMAC pain VAS A1 subscale (walking on a flat surface) will be selected as the target knee; 5. Pain ≥50 mm on the WOMAC pain VAS A1 subscale (walking on a flat surface) in the target knee; 6. Patients having discontinued use of all systemic analgesic/non-steroidal anti-inflammatory drugs (NSAIDs) therapy for at least 7 days (24 hours for paracetamol) prior to the screening visit and agree not to resume them during the investigation. Note: paracetamol will be provided to patients as rescue medication. 7. If female of child-bearing potential, must have a negative urine pregnancy test at the screening visit and use a reliable form of contraception for more than 1 month prior to Screening and throughout the investigation. Note: to be considered females of non-child- bearing potential, females must be surgically sterile or postmenopausal as documented in medical history for at least 1 year. Highly effective birth control methods include: combined hormonal contraception (containing estrogens and progestogen) associated with inhibition of ovulation (oral, intravaginal, transdermal); progestogen-only hormonal contraception associated with inhibition of ovulation (oral, injectable, implantable); intrauterine device (IUD); intrauterine hormone-releasing system (IUS); bilateral tubal occlusion; vasectomised partner; sexual abstinence.\* * Note: According to 4.1 paragraph "Birth control methods which may be considered as highly effective" of the Clinical Trial Facilitation Group (CTFG)/Recommendations related to contraception and pregnancy testing in clinical trials. Exclusion Criteria: 1. Radiographic assessment confirming abnormal patellofemoral tracking or articulation or abnormal/excessive patellar subluxation in lateral view; 2. Major injury to or disorder of the contralateral knee or other weight-bearing joint that would interfere with the study assessments; 3. Secondary OA due to a prior or concomitant condition (e.g., septic arthritis, inflammatory joint disease, gout, articular fracture, major dysplasia, or congenital abnormality, hemochromatosis, etc.); 4. Patients who have had arthroplasty at the target knee at any time; 5. Surgery in the target knee within the previous 12 months prior to Screening or any planned surgery throughout the duration of the investigation; 6. Surgery in the contralateral knee or other weight-bearing joint within the previous 12 months that would interfere with the study assessments; 7. Patients that are candidate for knee replacement within the next 12 months; 8. Patients having had diagnostic or surgical knee arthroscopy, or knee lavage in the target knee in the 6 months prior to the screening visit, or patients in which such procedures are planned during the study; 9. Patients with total joint replacement implants, unicondylar implants or patellofemoral replacement implants in the study joint; 10. Ligament reconstruction of the target knee in the previous 3 years; 11. Inflammatory arthropathies such as rheumatoid arthritis, lupus, or psoriatic arthritis; 12. Patients with clinically relevant intra-articular effusion of the target knee; 13. Episode of gout or calcium pyrophosphate (pseudogout) diseases within 6 months prior to Screening; 14. Patients having received: * Corticosteroids by systemic administration within 30 days prior to the screening visit. Inhaled corticosteroids are permitted if the Subject has been on a stable regimen for the past 1 month prior to Screening and remains on this regimen throughout the course of the investigation; * Analgesic/NSAIDs by systemic administration within 7 days prior to the screening visit; * Intra-articular drugs within 12 weeks prior to the screening visit; * Chondroitinsulphate, glucosamine, diacereine, bisphosphonates or matrix metalloproteinase (MMP) inhibitors within 30 days prior to the screening visit; * Viscosupplementation of the target knee within 6 months prior to the screening visit; * Paracetamol in the 24 hours prior to the screening visit; * Treatment with any other investigational product within 3 months prior to the screening visit. 15. History of allergic reaction to an intra-articular Hyaluronic acid injection; 16. Known hypersensitivity (allergy) to gram positive bacterial proteins; 17. Inability to perform the Timed Up and Go (TUG) test; 18. X-ray findings of acute fractures, severe loss of bone density, avascular necrosis and/or severe deformity; 19. Axial deviation of the lower limbs greater than 20 degrees in valgus or varus on standing X-ray, ligamentous laxity, or meniscal instability as per study investigator(s); 20. Significant surgery of lower limbs (hip, ankle, foot) that may interfere with knee assessments; 21. Patients with any musculoskeletal condition affecting the target knee that would impair assessment of the effectiveness in the target knee (e.g. Paget's disease of bone); 22. Patients with significant pain outside the target knee, including significant hip or back pain; 23. Chronic use of analgesia for pain (including pain in the other knee or any other joint) that may interfere with the evaluations of the test knee (such as possible use of rescue medication for these other conditions); 24. Known allergies to paracetamol and hyaluronan preparations; 25. Recurrent medical history of severe allergic or immune-mediated reactions; 26. Active infection or skin diseases in the area of the potential injection site or joint; 27. Any dermatological disease overlying the study joint that would contraindicate injections or aspirations; 28. Peripheral neuropathy that would be severe enough to interfere with the evaluation of the subject; 29. Psychological status (e.g., anxiety, depression, poor sleep quality, pain catastrophizing, etc.) that may interfere with functional assessment of the target knee; 30. Vascular insufficiency of lower limbs that is severe enough to interfere with the evaluation of the subject; 31. Any concomitant disease(s) or condition(s) that may interfere with the free use and evaluation of the affected knee for the 12 months course of the investigation (cancer, other rheumatic diseases, gout, severe congenital defects, etc.); 32. Continued participation in an experimental drug/device study or any clinical trial within the previous 8 weeks prior to Screening. Subjects must have fully completed participation in an experimental drug/device study of any clinical trial at least 8 weeks prior to screening; 33. Pregnancy, breastfeeding, planned conception, premenopausal women who have not had tubal ligation, hysterectomy, or are unwilling or unable to utilize contraceptive measures (or contraception); 34. Prior history of any malignancy with the exception of basal cell carcinoma of the skin treated more than 2 years prior to Screening; 35. Significant bleeding diathesis; 36. Patients who are not able to comply with study procedures or who are likely to be noncompliant or uncooperative during the study according to the investigator's opinion.