Patients are prospectively evaluated basally and at 2, 6, and 12 months of follow-up using IKDC, KOOS, EQ-VAS for general health status, and Tegner scores. Furthermore at basal evaluation and at every follow-up the ROM and the transpatellar circumference of both the index knee and the contralateral one are measured to check if any changes occurred over time. Patient satisfaction and adverse events will be also reported. All the clinical evaluations are performed by a medical staff not involved in the injective procedure, in order to keep the study double blinded. At the end of the study, the nature of the injected substance is revealed to the patients.