To compare the efficacy and safety of topical tranexamic acid versus placebo in patients diagnosed with severe knee osteoarthritis who will undergo prosthetic knee surgery in terms of saving blood loss (estimated blood loss, decreased hemoglobin and Decrease in hematocrit).

Tranexamic acid (Amchafibrin) exerts an antihemorrhagic activity by inhibiting the fibrinolytic properties of plasmin. Tranexamic acid binds to plasminogen when it is transformed into plasmin. The activity of the tranexamic acid-plasmin complex on fibrin activity is less than the activity of free plasmin alone.

There are two methods of presentation: one, as an injectable solution; Two as a clear, colorless aqueous solution.

Tranexamic acid in Spain is approved for use in the prevention and treatment of bleeding due to general fibrinolysis. As for its specific indications the investigators find that it is used for the treatment of metrorrhagia, menorrhagia, gastrointestinal hemorrhage, urinary hemorrhagic disorders after prostate surgery, surgery of ears, nose, throat, gynecological, thoracic, abdominal or cardiovascular or to counter associated hemorrhages To the administration of a fibrinolytic drug.

Inclusion Criteria:

• Patients of both sexes, in the age group: ≥18 and ≤80 years.
• Patients diagnosed with confirmation of severe knee osteoarthritis according to Kellgren criteria (equal or greater than 2) and EVA greater than 7, who will be subjected to knee arthroplasty surgery.
• Patients signing informed consent, agreeing to participate in the study.

Exclusion Criteria:

• Patients with concomitant cardiac disease: unstable angina pectoris, acute myocardial infarction, atrial fibrillation, flutter, history of sudden death, severe valve insufficiency.
• Patients with concomitant previous thromboembolic disease: Deep venous thrombosis, pulmonary thromboembolism, thrombotic arterial embolism, Ischemic Vascular Cerebral Stroke, fibrinolytic diseases after consumption coagulopathy.
• Hypersensitivity to tranexamic acid.
• Severe systemic disease: cardio-pulmonary, neurological, renal, infectious or any other type that may impede the development of the study or evaluation of the results.
• History of seizures.
• Patients with severe mental disorder (psychotic disorder, risk of autolysis, manic episode), dependence on toxic substances and / or some physical or psychological limitation to answer.
• Patients receiving oral anticoagulants.
• Patients in litigation for disability claim related or not with the disease.
• Patients who cannot make the necessary visits to carry out the study.
• Patients who refuse to participate or sign informed consent.
• Pregnant and lactating patient's period.