Jordy van Sambeeck

Dutch translation and validation of the NPI score and the BPII 8 131 its usefulness. The best PROM pertaining to patellofemoral instability patients has yet to be found. This is mandatory to quantify the disability and impairment, evaluation after treatment and mid- and long- term follow up after surgery. Competing interests We have received no funding for this study and have no competing interests to declare. Authors’ contributions SK initiated the study by defining the research question and purpose of the study. JvS performed data collection and analysis and drafted the manuscript. SK was the first author to review drafts of the manuscript and gave final approval of the version to be submitted. SvdG was second reviewer of drafts of the article and added important feedback for interpretation of the results and for discussion section. Acknowledgements We thank Daniël Haverkamp who collaborated as an advisor for the design of the study protocol.