 It is currently unknown how this high risk comes about considering its short duration and minimal tissue damage caused by the procedure. A factor that may play a role is the use of a tourniquet. A large majority of orthopaedic surgeons prefer to operate within a dry field, which is obtained by the use of a tourniquet. In the proposed study the investigators will investigate the effect of a tourniquet on local and systemic markers of hypoxia, inflammation, involvement of endothelium, and coagulation activation. 