<qa>  What is the maximum amount of blood obtained from the forearm?Group 2. In the preoperative room with previous premedication, a total of 55cc of total venous blood is obtained from the forearm cubital o basilic veins. The blood is carried on 12 steriles tubes using sodium citrate at 3.8 as anticoagulant BD, Vacutainer; Becton, Dickinson and Company, NJ. Blood samples are then transported to the Bank of Tissue Banco de hueso Dr. José E. Gonzalez where by centrifugation at 1800 rpm for 10 minutes HeraeusMegafuge 1.0R; ThermoElectronCorporation the separation of the 3 layers White, yellow and red. The superior layer rich in plasma will be collected in 50 microliters polypropylene tubes Corning,NY. A final volumen of 16 ml of platelet rich plasma is obtained and will transferred to airtight tubes BD Vacutainer; Becton, Dickinson and Company, NJ. The manipulation of the blood samples is made on laminar flow cabin biosecurity class II Logic 3440801; Labconco, KC. The platelet rich plasma will be activated with calcium gluconate at 10 Pisa Farmacéutica, Jalisco, México before using it is placed in the surgical site topically. The PRP simple will be divided in two applications, initiating the intervention after the final cuts of the TKR components like the tranexamic acid group. 