80 patients diagnosed with knee osteoarthritis were randomized into two groups: patients in Group 1 received a single intraarticular injection of PRP whereas those in group 2 were administered three intraarticular injections of PRP within an interval of 2 weeks between each application. Patients were evaluated before the treatment and at the 6 month after the treatment with a Visual Analog Scale (VAS) and The Western Ontario and MacMaster Universities (WOMAC) Osteoarthritis Index.

Inclusion Criteria:

• ages of 35 and 80
• Kellgren-Lawrence grade of 2, 3, or 4

Exclusion Criteria:

• rheumatic diseases, coagulopathies, severe cardiovascular diseases, local infections, malignancies, immunodeficiency, schizophrenia, mental retardation, anticoagulant therapy, a hemoglobin concentration of 11 g/dL and platelets of 150,000/L, a history of severe trauma, or a history of hyaluronic acid or corticosteroid injection within the previous 6 months