Diabetes and increased body mass index are two of the most associated comorbidities in patients undergoing total knee arthroplasty. With the number of patients undergoing knee arthroplasty increasing and with the incidence of diabetes and increased BMI, we can expect that in the coming decades the association of the two comorbidities will be frequent. An ethical issue arises when the patients who are refused for total knee arthroplasty are instructed to change the risk factors, and they fail either because of a mental problem or because of a physical problem. This study analyzes the effects of controlled, uncontrolled, uncomplicated and complicated diabetes on the rates of post- knee arthroplasty complications. The study proposes to evaluate obese patients in terms of functional outcomes and postoperative complications after total knee arthroplasty.