Inclusion Criteria:  patients older than 50 years a diagnosis of primary knee osteoarthritis Kellgren-Lawrence (K-L) grading scale smaller than 3 both male and female.  Exclusion Criteria:  patients younger than 50 years of age K-L grade 3 or more history or active presence of clinically significant inflammatory articular or rheumatic disease other than OA generalized OA the detection of rapidly progressive OA before the start of the trial underwent any previous lower extremity surgery excessive mechanical axis deviation (varus > 5°, valgus > 5°) body mass index larger than 30 history or presence of malignant disorders systemic disorders such as diabetes mellitus, severe cardiovascular diseases, hematologic diseases, immune-deficiencies, and infections systematic or intra-articular corticosteroid therapy in the previous 3 months prior treatment with HA in the past 6 months anticoagulants or antiaggregants therapy in the preceding 30 days non-steroidal anti-inflammatory medications in the preceding 7 days platelet count less than 150,000/ml of blood hemoglobin values less than 12g/dL of blood.