Introduction: The human foot is a complex multi-articular mechanical structure and one of the most complex structures in the human body, playing an extremely important role in the biomechanical function of the movement. The development of feet takes place on different levels which comprise structural and functional maturation processes. Foot posture can be assessed through a variety of measures including plain film radiographs, static foot posture measures and footprint analysis. No universally accepted clinical measure for assessing, evaluating and monitoring high – prevalent paediatric flat foot and the development of medial longitudinal arch was found within existing literature. Purpose: The aim of this study was to examine the intra-rater reliability of different measures for paediatric foot posture and to determine which of them is the most suitable for assessment in school children. Methods: 108 participants were included in this study. Three measures of foot posture – Foot Posture Index, Navicular Drop test and paper footprint analysis using podograph were performed twice. Testing sessions were separated by one week. Assessment of intra-rater reliability was conducted using intraclass correlation coefficients. Paired t-test was performed to compare separate measures and standard errors of measurement (SEM) and minimal detectable change (MDC) were calculated. Differences between age groups were analyzed with a one-way analysis of variance (ANOVA). Results: Intra-rater reliability of Foot Posture Index (FPI-6) was excellent in all age groups (ICC>0,9) followed by reliability of Chippaux-Smirak Index (CSI) and Staheli Index (SI). Reliability for those was excellent in all groups except in the youngest age group, where the reliability was good. Reliability of Navicular Drop Test (NDT) was good in all age groups. When comparing different age groups there are significant differences (p<0,05) in outcomes in all measures except NDT. Discussion and Conclusion: The outcomes of this study suggest that FPI-6 should be the preferred method of paediatric foot posture measurement in future research in school children. Findings suggest CSI, SI and NDT are also appropriate when assessing foot posture. There are significant differences in outcomes between age groups with higher reliability in older children. Future research should examine other measurement properties of measures - inter-rater reliability of these measures, validity (construct and concurrent) as well as examine correlation between measures.
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