BACKGROUND:In Asia, obesity has reached epidemic proportions and physicians are likely to face a burden of obesity-related disorders, of which osteoarthritis of the knee is one. However, it is unclear whether obesity affects improvement of conventional TKAs in Asian patients. PURPOSE:We therefore asked whether obese patients with a BMI of 30 kg/m(2) or greater would have worse ROM and function after TKA compared with their nonobese counterparts and whether they would have less improvement preoperatively to postoperatively. METHODS:We retrospectively reviewed 369 patients who underwent TKAs from 2006 to 2010. We stratified patients into four groups: (1) 98 patients with BMIs less than 25 kg/m(2); (2) 158 patients with BMIs between 25 kg/m(2) and 29.9 kg/m(2); (3) 87 patients with BMIs between 30 kg/m(2) and 34.9 kg/m(2); and (4) 26 patients with BMIs greater than 35 kg/m(2). We then compared ROM, function score, Knee Society score, Oxford Knee Questionnaire, and SF-36 questionnaire(®) across the four groups at 6- and 12-month follow-ups. RESULTS:At the 6-month followup, we found a difference only in the ROM. At the 2-year followup, there were no differences in any functional scores across the four groups. Severely obese patients had greater improvement in postoperative ROM than the other groups but did not have any greater improvement in function. CONCLUSION:BMI had little clinical impact on short-term outcomes of conventional TKAs in Asian patients. The data suggest that BMI should not be used as a major determinant to exclude obese patients from surgery with the presumption of poorer outcomes.