Crosscultural Adaptation and Validation of the Korean Version of the New Knee Society Knee Scoring System.

BACKGROUND: The 2011 Knee Society Score© (2011 KS Score©) 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 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). For validity, three of the four domains (the exception was expectation) of the 2011 KS Score, correlated either strongly or moderately with the Korean WOMAC score (r ≥ 0.35). When compared with the SF-36, the satisfaction domain showed a weak positive correlation with all the subscales of the SF-36 except general health (r < 0.35). The activity domain showed a strong positive correlation with physical function (r = 0.62) and physical component summary (r = 0.52), moderate with physical role (r = 0.46), and weak with bodily pain (r = 0.26) and social function (r = 0.31). The symptom domain also exhibited a similar moderate positive correlation with physical function (r = 0.41) and weak positive correlation with bodily pain, social function, and physical component summary (r = 0.22, 0.20, and 0.26, respectively). For responsiveness, all the domains of Korean version of the 2011 KS Score, except for expectation, showed large changes (> 0.8), calculated as standardized response mean. The total amount of the Korean version of the 2011 KS Score (2.03, p < 0.001) showed higher responsiveness when compared with the WOMAC total (1.88, p < 0.001) and SF-36 physical and mental component summaries (1.14, p < 0.001; and 0.68, p < 0.001, respectively).
CONCLUSIONS: The Korean version of the 2011 KS Score was successfully developed using a process of crosscultural adaptation for the Korean-speaking population who had undergone TKA for osteoarthritis of the knee. The Korean version of the 2011 KS Score was shown to be a reliable, valid, and responsive tool and can be used to assess functional outcomes and expectations of Korean patients who undergo TKA. The demographic features of TKA in the Korean population should be taken into account with additional studies recommended to further investigate these psychometric properties in Korean men. LEVEL OF EVIDENCE: Level II, diagnostic study.