Background The 2011 Knee Society Score Ó (2011 KS Score Ó ) is used to characterize the expectations, symptoms, physical activity, and satisfaction of patients who undergo TKA and is widely used to assess the outcome of TKA. However, it has not been adapted or validated for use in Korea.Questions/purposes We developed a Korean version of the 2011 KS Score and evaluated the (1) test-retest reliability, (2) convergent validity, and (3) responsiveness of the Korean version. Methods The Korean version of the 2011 KS Score was derived by using a well-established translational procedure based on international guidelines, which include translation, synthesis, back-translation, expert committee review, pretesting, and submission for appraisal. A total of 123 patients with knee osteoarthritis who were scheduled to undergo TKA were recruited for the study. Ninety percent of the patients (111 of 123) were women, which is an exact representation of the Korean population having TKAs. To evaluate reliability, the patients were evaluated twice during a 4-week interval using the questionnaire. Reliability was assessed by using intraclass correlation coefficients (ICCs) and internal consistency by using Cronbach's alpha to determine the validity of the Korean version of the 2011 KS Score. The patients were evaluated by using the validated Korean versions of the WOMAC and SF-36 questionnaires. Spearman's correlation coefficient was used for validation. Responsiveness was determined by calculating the standardized response mean from the preoperative and postoperative test scores in One of the authors certifies that he (TKK) has or may receive payments or benefits, during the study period, an amount of USD 10,000-USD 100,000, from Smith & Nephew, Inc (Seoul, Republic of Korea). All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research 1 editors and board members are on file with the publication and can be viewed on request. Each author certifies that his or her institution approved or waived approval for the human protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research. This work was performed at the Joint Reconstruction Center, Seoul National University Bundang Hospital, Gyeonggi-do, Republic of Korea. the Korean version of the 2011 KS Score. To address the gender disparity in our study we identified 53 males who underwent TKA for osteoarthritis after completion of this study and generated age-matched controlled groups to evaluate construct validity and responsiveness in Korean males. Results The reliability proved good to excellent with an ICC between 0.69 and 0.85, depending on the clinical properties tested, which included the following: symptoms, satisfaction, expectation, and total functional activity consisting of functional activity, standard activity, advanced activity, and discretionary activity. All subscales showed good to excellent internal consistency indicated by Chronbach's alpha (range, 0.83-0.92 Ele...