Inclusion Criteria:

• Male subjects aged 18 years or above and postmenopausal female subjects
• Subjects scheduled for elective total knee replacement
• Subjects written informed consent for participation after receiving detailed written and oral information previous to any study specific procedures

Exclusion Criteria:

Related to medical history:

• Any prior DVT or PE
• Myocardial infarction (MI), TIA or ischaemic stroke within the last 6 months prior to randomization
• History of heparin-induced thrombocytopenia, allergy to heparins
• Intracerebral or intraocular bleeding within the last 6 months prior to randomization
• History of gastrointestinal disease (e.g. active peptic ulcer) with gastrointestinal bleeding within the last 6 months prior to randomization
• History or presence of gastrointestinal disease which could result in an impaired absorption of the study drug (e.g. severe active inflammatory bowel disease, short gut syndrome)
• Amputation of one leg

Related to current symptoms or findings:

• Heart insufficiency NYHA III-IV
• Congenital or acquired haemorrhagic diathesis (PT INR/aPTT not within normal limits)including patients with acquired or congenital thrombophilia
• Thrombocytopenia (platelets < 100,000/µl)
• Macroscopic haematuria
• Allergy to contrast media
• Severe hypertension (SBP > 200mmHg, DBP > 100 mmHg)
• Impaired liver function (transaminases > 2 x ULN)
• Impaired renal function (serum creatinine > 1.5 x ULN or decreased creatinine clearance < 30ml/min)
• Active malignant disease
• Presence of active peptic ulcer or gastrointestinal disease with increased risk of gastrointestinal bleeding
• Body weight < 45 kg
• Drug- or alcohol- abuse

Related to current treatment:

• Therapy with oral anticoagulants (e.g. phenprocoumon, warfarin-sodium, heparins and factor Xa inhibitors other than study medication) and fibrinolytic therapy
• Therapy with acetylic salicylic acid or other thrombocyte aggregation inhibitors (e.g. clopidogrel, dipyridamole and ticlopidine) should be stopped one week before enrollment. Patient not able to stop ASA therapy will be excluded
• All other drugs influencing coagulation, (exception: NSAIDs with half life < 17 hrs will be allowed)
• Systemic and topical treatment with azole compounds (e.g. ketoconazole, fluconazole, itraconazole). Azole compounds should be stopped at least four days before enrollment

Miscellaneous:

• Planned intermittent pneumatic compression during active treatment period
• Planned epidural anaesthesia with indwelling epidural catheter (spinal and epidural anaesthesia without indwelling catheter is allowed)
• Therapy with another investigational product within 30 days prior to the start of the study
• Concomitant participation in another trial or study

Removal of Subjects from Study:

A subject who withdraws is one who discontinued a clinical study for any reason.

Subjects may be withdrawn from the study for the following reasons:

• At their own request or at the request of their legally acceptable representative
• If, in the investigator's opinion, continuation in the study would be detrimental to the subject's well-being
• At the specific request of the sponsor