Intraarticular Leukocyte-rich and Leukocyte-poor PRP for Osteoarthritis of the Knee

Inclusion Criteria: * Age greater than or equal to 50 years old, Plain radiographs knee AP shows Kellgren-Lawrence classification 1-4, Refuse the use of NSAIDs for 2 weeks. Exclusion Criteria: * 1\) Previous intra-articular injection therapy in the past 6 months; 2) Previously treated with intra-knee PRP injection; 3) History of knee arthritis from other causes such as rheumatoid arthritis, pseudogout or infectious joints 4) History of blood disorder including anemia and thrombocytopenia (Hb \< 12 g/dl, plt \< 150,000/ml ) 5) History of surgery on the aforementioned knee 6) Obvious knee deformity (valgus \> 15, varus \> 20, flexion ROM \< 90 , extension lag \> 20) 7) Pregnancy and lactation