Is retrospective application of the Oxford Shoulder Score valid?

This study shows that individual patient recall of symptoms was variable. There is considerable disagreement between their original and recalled scores. However, when applied to a large group, recollection of shoulder symptoms as assessed by the OSS was not subject to recall bias. It is, therefore, possible to use the mean value of recollected scores, within a population, to assess the impact of an intervention. For example, following shoulder trauma where a prospective measurement is not possible.