Primary aim of this trial was to assess, among patients with grade II/III osteoarthrosis of the knee, efficacy (as determined by improvement at MRI 6 months after the first injection) of three intraarticular injections of platelet lysate when compared to hyaluronic acid. Additional objectives were to compare the treatment groups in terms of a number of functional scales (WOMAC, Lysholm, Tegner Knee, Scale, AKS, Lequesne, VAS) and of number of adverse events.