The purpose of this study is to compare the blood loss of intravenous and topical administration of low dose epinephrine plus combined administration of intravenous and topical tranexamic acid for primary total knee arthroplasty.

Inclusion Criteria:

• All patients between the ages of 20 and 75 who were diagnosed with osteoarthritis of the knee and scheduled for an elective primary total knee arthroplasty and those who were willing and able to return for follow-up over at least a 6-month postoperative period

Exclusion Criteria:

• Acute coronary syndrome < 6 months
• Glaucoma,pheochromocytoma, thyrotoxicosis, digoxin intoxication, serum potassium < 3.0 mmol, alcohol abuse, premenopausal women
• Current treatment with adenosine diphosphate (ADP) receptor antagonists, Factor Xa or thrombin inhibitors,heparin (excluding Low Molecular Weight Heparin (LMWH) for perioperative thromboprophylaxis), tricyclic antidepressants, or monoamine oxidase（MAO) or Catechol-O-methyltransferase (COMT) inhibitors
• Patients with history of thromboembolic disease, bleeding disorder
• Patients with history of renal impairment, cardiovascular diseases (previous myocardial infarction, atrial fibrillation) or cerebrovascular conditions (previous stroke or peripheral vascular surgery)
• Allergy to TXA