Introduction: There is an overwhelming need for worldwide applicable subjective grading systems for patients' anterior cruciate ligament (ACL) tear. The scoring system should be validated for their use in advance related measurements. For the Indonesian language speaking population, only the Kujala Patellofemoral Score (KPS) questionnaire has been translated and validated into the Indonesian language for diseases related to knee pain, but none for ACL tears. The present study aims at cross-cultural adaption to measure the validity and reliability of the Kujala patellofemoral score Indonesian version (KPS-I) specifically for ACL tear patients. Material and methods: The responses of 106 ACL tear patients on two questionnaires comprising the KPS-I and Short Form (SF)–36 were examined by determining the validity and reliability. We conducted the validity construct and content, so the reliability was evaluated by test-retest reliability, internal consistency and measurement error. In addition, the research utilised the Bland and Altman method to explore absolute agreement. Results: The construct and content validity were good, where all hypotheses were confirmed, and the floor or ceiling effect did not occur. The reliability proved excellent between test and retest (ICC=0.99). An internal consistency showed a good Cronbach α of 0.86. The standard error of measurement (SEM), minimal detectable change at the individual (MDCind), and minimal detectable change at the group (MDCgrp) were determined to be 2.1, 5.8, and 0.7, respectively. The application of the Bland and Altman plot method revealed no bias in this study. Conclusion: The validation procedure shows that the KPS-I is a good evaluation instrument for Indonesian patients with ACL tear. However, it is suggested that this score be used for follow-up of patients after ACL reconstruction procedure, especially with anterior knee pain related to the original objective of the Kujala score.