Acute coronary syndrome (ACS) presents today the leading group of post-operative cardiovascular complications, while endothelial dysfunction (ED) is one of the key elements in its development. The chronic ED represents thus the basis for the gradual development of atherosclerotic changes, while its sudden aggravation leads to ACS. The persistent ED occurs due to the effects of chronic cardiovascular risk factors, while according to the available studies it can also develop or aggravate under the impact of different acute events. We have directed this study to the investigation of the dynamic of endothelial function before and after a major orthopaedic surgical intervention. This randomised prospective study included 19 patients that underwent the intervention of total knee replacement and 20 healthy examinees of the adequate age and gender High-resolution ultrasound test based on the flow mediated dilatation of the brachial artery is what at we carried out at the beginning of the research, respectively 12, 24, 48 and 72 hours, as well as 7 days after the surgical intervention. The starting values of the FMD test were within the normal range in both groups, although the ability of dilatation upon stimulus was significantly lower in the investigated group. The FMD percentage change in the total sample was negatively connected with the body weight, not having shown additional connections with other cardiovascular risk factors. During the early post-operative period, a significant transitory lowering of the FMD percentage change was recorded, having reached the lowest value 24 hours after the surgery. During the seven-day prospective surveillance, no significant cardiovascular complications were recorded. Further research is necessary in order to confirm these results as well as the testing of the possible connection of the described post-operative transitory endothelial dysfunction with the development of cardiovascular complications and the adverse event.