Study of the Prognostic Value of the Coagulolytic Balance Dependent on Circulating Microvesicles in the Occurrence of Thrombotic Events After Total Knee Replacement in Orthopedic Surgery.

Inclusion Criteria: * Subject, male or female, aged 18 to 85 years (upper age limit classically used in the literature of PTG79-81) * First-line TKP (knee native to any prosthesis) performed to treat primary or secondary osteoarthritis. In case of contralateral PTG, a delay of 12 months between the 2 prostheses will be respected according to the habits of the inclusion centers. * ASA score \<4 (American Society of Anesthesiologists) * No contraindication to prophylactic treatment with low molecular weight heparin (LMWH) * Subject not taking anticoagulant or antiaggregant therapy at therapeutic dose * Subject who has signed the informed consent form * Subject affiliated to the social security system Exclusion Criteria: * Subjects with a history of sepsis, tumor or trauma in the considered joint * Subject with sepsis or acute infection * Immunocompromised subject (HIV, transplant, chemotherapy, leukemia, glucocorticoids \>3 months) * Subjects with severe respiratory, circulatory or cardiac pathologies involving anticoagulant treatment likely to influence the coagulolytic balance. * Subject with severe renal insufficiency (creatinine clearance \< 30ml/min) * Subject refusing to participate in the study or not signing the informed consent or unable to adhere to the study procedures * Subjects who are minors, pregnant or breastfeeding, not affiliated with the social security system, or deprived of liberty * Subject already included in an interventional trial (which may alter the results of that study)