The Banff Patellar Instability Instrument: validity and reliability of an Indonesian version

Background: The Banff Patellar Instability Instrument (BPII) is a valuable scoring tool for assessing patellofemoral instability in patients suffering from patellofemoral pain syndrome (PFPS). The BPII 2.0 is a shortened version of the BPII. However, there is no Indonesian edition of BPII 2.0 that has been validated. This study aimed to determine the validity and reliability of the Indonesian version of the BPII 2.0. Materials and methods: This was a cross-sectional study that used a forward–backward translation protocol to create an Indonesian version of the BPII 2.0. Thirty patients with PFPS were given the questionnaires. The questionnaire's validity was evaluated by analyzing the correlation between score of each subscale and the overall score to the Indonesian version of the Kujala score using Pearson correlation coefficient, while the reliability was evaluated by measuring the internal consistency (Cronbach α) and test–retest reliability (intraclass correlation coefficient). Results: The Indonesian version of BPII 2.0 and the Indonesian version of Kujala score had a strong Pearson correlation coefficient for construct validity. For all subscales, Cronbach α was 0.90–0.98, indicating adequate internal consistency. The test–retest reliability was high, with intraclass correlation coefficient ranging from 0.89 to 0.98 for all subscales. There was no difference in the Indonesian version of BPII 2.0 response between the first and second administration of the questionnaire which was taken 7 days afterward. Conclusion: The Indonesian version of BPII 2.0 was determined to be valid and reliable and is therefore an objective instrument to evaluate patellofemoral instability in patients with PFPS in the Indonesian population.