The correct balance between risk factors for the patient and those related to the type of surgery performed is an essential requirement when proposing appropriate anti-thrombosis prophylaxis, which is not always without risks. The guidelines consist in the essential parameter with which the surgeon must be inspired. Nonetheless, their acceptance cannot be totally uninfluenced but must be submitted to a critical analysis, as it cannot constitute, in terms of so-called defensive medicine, a hypothetical refuge to avoid responsabilities nor can it be an acritical parameter in a legal situation. In recent years, cases in this field have increased so that it seems useful to suggest greater involvement by the coagulation specialist, at least in the most complex cases. Legal suits frequently involve a lack of prophylaxis, inadequate prophylaxis, lack of monitoring of coagulative parameters, insufficient duration of prophylaxis, lack of diagnostic testing to be used when DVT and PTE are suspected. Nonetheless, in order to avoid blame on the profession it is not enough to choose suitable and correct treatment; it is important to also keep iatrogenic injury from becoming the center of a legal action because of the lack of patient informed consent. The amount of data is directly proportional to the amount of risk. Furthermore, it is necessary to insist on the need to document data, as a preventive measure, so that the patient is also responsible for the risk taken. In court, the signing of forms cannot be valid proof that the patient was effectively and truly provided with all of the information required.