120 patients with knee osteoarthritis with a specific age range and duration of symptoms more than 3 months and having Inclusion criteria, are included in the study. Evidence and method of injection of PRGF, Ozone, PRP and HA, as well as the potential benefits and complications of the study are presented by a physiatrist. Patients are screened at the first visit, including history, physical examinations, laboratory requests (CBC, ESR, CRP) and knee AP and Lateral x-Ray view in standing position and patient medications. Then patients are randomized to four groups receiving PRGF, Ozone, PRP, and HA. For each group appropriate exercise therapy is prescribed . At the beginning of the study, and in order to measure the outcome of the patients in the 6th and 12th months after the completion of the injections, WOMAC and VAS questionnaires were used to assess joint stiffness, functional limitation and pain intensity.