Cross-cultural translation of the Lysholm knee score in Chinese and its validation in patients with anterior cruciate ligament injury

Translation of the English original Lysholm knee score followed previously published guidelines [19, 20]. The entire process consisted of five steps: 1) Forward translation from English to Chinese by two bilingual translators independently, who are native Chinese speakers and well conversant in English. One of the translators is an orthopedic surgeon in our department (the author, WW), the other is a full-time translator (RL) with no medical background, and is not informed of our investigation; 2) Revision and modification of the questionnaire regarding language expressions and cultural differences was discussed by the two forward translators and other research members. A primary version of C-LKS was then obtained; 3) Backward translation by two independent native English translators (FA and GD) who are well conversant in Chinese. The primary version of C-LKS was translated from Chinese to English. The two translators had medical backgrounds, with no knowledge of the original Lysholm knee score; 4) All researchers and translators convened and had discussions to solve any discrepancies, ambiguities and other language expression issues that existed in the questionnaire, and the pre-final version of C-LKS was obtained; and 5) Twenty patients with ACL injuries patients were invited to complete the pre-final C-LKS for assessment, and feedbacks were collected. The researchers met once more to make final adjustments according to these feedbacks and the final version of C-LKS was obtained.

Owing to the fact that the Lysholm knee score was initially designed for patients with ACL injuries [8, 15, 21], we also recruited patients with ACL injuries to minimize deviations. Cases involved in the present study were mainly recruited among patients with ACL injuries scheduled for arthroscopic ACL reconstruction at our hospital [22]. Our inclusion criteria were: Aged over 16 years old with independent signing authority; Chinese as the first language with adequate capability to read and complete a questionnaire; and a definitive diagnosis of ACL injury as determined by arthroscopy [21]. Patients with other complicated knee injuries, such as meniscal injuries or patellar dislocation; with a history of lower limb or spine surgery; patients who had surgery within a month of the study; and patients with a history of systemic disease and/or malignancy, were excluded from this study. Our study met the quality criteria proposed by Terwee and associates [23] for measurement properties of health status questionnaires, which required the results from at least 100 patients to perform internal consistency analysis and from at least 50 patients for floor or ceiling effects, reliability, and validity analyses. All patients involved in the study had thoroughly read and signed the informed consent. This study was approved by the ethics committee in the local hospital (No. CHEC2013-199).

The patients provided demographic information, such as sex, age and weight, on the first day of enrollment and independently completed the four questionnaires, C-LKS, WOMAC, IKDC, and Medical Outcomes Study Short-Form 36 (SF-36) in a quiet meeting room, followed by a C-LKS again 1 week later before receiving reconstruction surgery, in order to evaluate the test-retest reliability of the questionnaire. Patients were also reached via mail or telephone 6 months postoperatively to complete the C-LKS a time to help evaluate the responsiveness of the questionnaire.

The Lysholm knee score had eight items that evaluated walking gait, frequency of knee locking, frequency of pain, stair climbing, need for external support, body stability, joint swelling, and squatting ability. A total score (ranged 0 to 100 points) was calculated from the patient’s answers that best reflected his/her functional state. A lower score was indicative of poor knee function [8].

IKDC, first published in 2001, consists of 10 dimensions and evaluates the clinical symptoms, activity states, and function of the patient. The answers are checked accordingly, and the final score (range 0 to 100 points) is then calculated by a certain formula. WOMAC is a self-reported questionnaire specifically designed to evaluate the functional state of the knee or hip. It consists of 24 items divided into three subscales, namely, Pain (5 items), Stiffness (2 items), and Physical functioning (17 items). The final score (range 0 to 96 points) is the sum of all items. Unlike the majority of other questionnaires, a lower score represents a better functional state of the joint. SF-36 is a generic questionnaire for quality of life comprised of 35 items and eight dimensions that evaluate mental health and physiological and social functioning. Each dimension has its unique scoring system, and the final score is converted to percentages. A lower SF-36 score suggests a poorer quality of life or functional state. The above three scales have existed Chinese versions and are proven with excellent reliability, validity and responsiveness [24‐26].

To evaluate the acceptability of the questionnaire in the general population, we asked each patient in our study cohort if they had any difficulties understanding the content. We also calculated the miss rate of every item, and a >5 % miss rate of a certain item suggested an existing problem regarding acceptability or comprehension [27]. We also recorded the average time required to complete the questionnaire.

A distribution of scores was analyzed to determine whether a ceiling or floor effect existed. A result of <30 % of either results was considered acceptable [21].

Reliability tests included evaluations for test-retest reliability and internal consistency. Test-retest reliability was performed by comparing the former two C-LKS results of which the evaluation norm was the intraclass correlation coefficient (ICC), which was derived from a two-way analysis of variance (ANOVA) in a random effects model. These results displayed good reliability when ICC > 0.6, and excellent reliability when ICC was >0.8 [28]. Cronbach’s alpha was used to evaluate internal consistency when it was >0.7, >0.8 and >0.9, the questionnaire was regarded as having acceptable, good and excellent internal consistency, respectively [23]. We further depicted Bland-Altman plots to observe for systematic error between the investigations [29, 30].

Validity tests were performed particularly evaluating content validity, construct validity and external validity. For content validity, a rehabilitation expert (QW) and three orthopedic experts (ZW, YK and the author WX) helped to assess the understanding and relevance of all of the items in the C-LKS. Good construct validity referred to a questionnaire that correlated well with measures of the same construct (convergent validity), while poorly correlated with measures of different constructs (divergent validity) [31]. Therefore, we initially assumed that the score of C-LKS should correlate well with the physical subscales (i.e. Physical Functioning, Role-Physical, and Bodily Pain) of SF-36, but correlate poorly with other subscales (Vitality, Role-Emotional, Mental Health, Social Function and General Health) of SF-36. Based upon such assumption, the Pearson’s correlation coefficient (r) of C-LKS with subscales of the SF-36, WOMAC and IKDC was calculated. The construct validity of C-LKS was evaluated by comparing the compatibility of the results with our initial assumption. The correlations were judged either as poor (r = 0–0.2), fair (r = 0.2–0.4), moderate (r = 0.4–0.6), very good (r = 0.6–0.8), or excellent (r = 0.8–1.0) [31]. We also calculated the Cohen’s Kappa (k) coefficient between the results of C-LKS and IKDC to evaluate external validity, and k > 0.60 was thought to be necessary for an acceptable external validity [32].

Finally, we evaluated the responsiveness of C-LKS by comparing questionnaire results before treatment and 6 months after treatment. Effect size (ES) and standardized response mean (SRM) were the two indices used to evaluate responsiveness. SRM was defined as the mean change between these time points divided by the SD of this change. ES was defined as the mean change between preoperative results and 6 month postoperative results divided by the SD of the preoperative C-LKS score [33]. A greater value of ES and SRM suggested a better responsiveness of C-LKS.