“…It is likely that these studies used a sample of convenience because this type of sampling involves the selection of the most accessible members of the target population [40]. Five studies [2,7,10,18,19] reported using a retrospective sample of convenience chosen from children who had already attended a health service such as a gait laboratory or orthopaedic outpatient unit. The main limitation of this sampling method is that the sample may be biased and not representative of the entire population of interest [40].…”