Background: No questionnaire is currently available for use in patients with anterior cruciate ligament (ACL) injuries in an Indonesian population. The most-used questionnaire in clinical research for these patients is the International Knee Documentation Committee (IKDC) Subjective Knee Form, as its psychometric properties are considered to be excellent. Purpose: To translate the IKDC into Indonesian and assess its validity for use in Indonesian-speaking patients with ACL injuries. Study Design: Cohort study (diagnosis); Level of evidence, 2. Methods: After a forward-and-backward translation procedure and cross-cultural adaptation, the validity and reliability of the questionnaire were investigated. The responses of ACL injury patients on 3 questionnaires, the Indonesian-IKDC (I-IKDC), 36-Item Short Form Health Survey, and Kujala Anterior Knee Pain Scale, were compared. Following consensus-based standards for the selection of health measurement instruments guidelines, construct validity, test-retest reliability, internal consistency, floor and ceiling effects, and measurement error were determined. The Bland-Altman method was used to explore absolute agreement. Results: Of 253 ACL injury patients, 106 (42%) responded to the invitation. Construct validity was considered good, as all predefined hypotheses on correlations between the I-IKDC and other scores were confirmed. Reliability proved excellent, with a high test-retest correlation (intraclass correlation coefficient = 0.99). Bland-Altman analyses showed no systematic bias between test and retest. Internal consistency was good (Cronbach α = .90). There were no floor or ceiling effects. Standard error of measurement was 2.1, and the minimal detectable change was 5.8 at the individual level and 0.7 at the group level. Conclusion: The I-IKDC, as developed, appeared to be a good evaluation instrument for Indonesian patients with ACL injuries.

Background: The Lysholm knee score and Tegner activity scale are frequently used patient-reported outcome measures in patients with anterior cruciate ligament (ACL) injuries because of their excellent psychometric properties. These questionnaires were originally developed in the English language. Purpose: To translate and cross-culturally adapt these measures into the Indonesian language and study their validity and reliability so that they can be used in the Indonesian-speaking population with ACL injuries. Study Design: Cohort study (diagnosis/symptom prevalence); Level of evidence, 2. Methods: After a forward-backward translation procedure and cross-cultural adaptation, validity and reliability were investigated. A total of 253 patients with an ACL injury were sent 4 questionnaires (36-Item Short Form Health Survey, Kujala anterior knee pain scale, Indonesian Lysholm knee score [I-LK], and Indonesian Tegner activity scale [I-TS]). The responses of those patients were analyzed. Following COSMIN guidelines, construct validity, test-retest reliability, internal consistency, floor and ceiling effects, and measurement errors were determined. The Bland-Altman method was used to explore absolute agreement. Results: A total of 106 patients (42% response rate) were included in this study. Construct validity was considered to be good, as more than 75% of the predefined hypotheses on correlations between the I-LK, I-TS, and other measures were confirmed. Reliability proved excellent, with a high test-retest correlation for both questionnaires (intraclass correlation coefficient = 0.99). Bland-Altman analysis showed no systematic bias between testing and retesting. The internal consistency of the I-LK was good (Cronbach alpha = 0.73). For the I-LK and I-TS, floor and ceiling effects were less than 15% (floor: 0% and 4.7%, respectively; ceiling: 12.3% and 3.8%, respectively); the standard error of measurement was 1.8 and 0.9, respectively; the minimal detectable change at the individual level was 5.1 and 0.6, respectively; and the minimal detectable change at the group level was 2.4 and 0.5, respectively. Conclusion: Both the I-LK and I-TS appear to be good evaluation tools for Indonesian-speaking patients with an ACL injury.