Total knee arthroplasty is often associated with excessive postoperative bleeding due to increased fibrinolysis. Hence, the objective of the proposed of this multicentre study is to determine the peri-operative bleeding comparing the application of topical and intravenous tranexamic acid with the habitual surgical haemostasis.

Objectives:

1. Principal: To assess if the topical and intravenous tranexamic acid reduce less or at least than 20% the blood losses with respect to the habitual haemostasia in patients, after unilateral total knee arthroplasty.
2. Secondary: To assess the treatment safety. To perform a cost- analyses.

Methods: Randomized, multicentre, open and parallel clinical trial with three comparative groups: Topical tranexamic acid, Intravenous tranexamic acid and habitual haemostasia. In all patients, a single drainage of 8mm will be inserted in the joint, and it will remain closed during one hour after the closure of the skin.

Nº of participant centres: 2. Random allocation will be centralised in "Hospital de la Santa Creu i Sant Pau".

Main outcome: Total blood loss (mL) in the post-operative period collected by the habitual drain system ).

Secondary outcomes: Total blood loss (mL)and hidden blood calculated by Nadler's formula. Proportion of patients with blood transfusion, complications of surgery wound, haemoglobin pre and post-operative, units of blood transfused, post-operative mortality, days of hospital stay, safety of interventions assessed.Direct cost analysis.

Substudy: Pharmacokinetic study. The first 24 patients included in "Hospital de la Santa Creu i Sant Pau" for tranexamic acid (12 topical- 12 intravenous) to determine:

1. Plasmatic concentrations of tranexamic acid
2. In topical and intravenous tranexamic acid administration determine the absorption rate and drug bioavailability by these routes: maximum plasma concentration, time to reach Cmax, AUC, and half-life.

Inclusion Criteria:

• Unilateral Total knee arthroplasty
• The patient consent to participate

Exclusion Criteria:

• Antecedent of thromboembolic disease
• Patient with cardiac alterations of the rhythm
• Patients with valvular cardiac prosthesis
• Patients with pro-thrombotic alterations of coagulation
• Treatment with anticonceptive drugs