Objective: The aim was to determine the interrater and intrarater reliability of navicular drop (NDP), navicular drift (NDT), and the Foot Posture Index-6 (FPI-6), and test-retest reliability of the static arch index (SAI) and dynamic arch index (DAI).

Methods: Sixty healthy individuals were assessed for intrarater and test-retest reliability. From 60 participants, 30 individuals were assessed for interrater reliability. A digital caliper was used to measure NDP and NDT. Electronic pedography was used to calculate SAI and DAI. The FPI-6 was also performed. All assessments were performed on the dominant foot. The NDP, NDT, SAI, and DAI were repeated 3 times. The NDP and NDT were analyzed separately using both first measurement and the average, but the SAI and DAI were analyzed using only the average. The NDP, NDT, and FPI-6 were conducted by 2 raters to determine interrater reliability and were repeated by a single rater after 5 days from initial assessment to determine intrarater reliability. The SAI and DAI were also repeated after 5 days to determine test-retest reliability.

Results: Intrarater intraclass correlation coefficients (ICCs) were 0.934 and 0.970 for NDP, 0.724 and 0.850 for NDT, and 0.945 for FPI. Interrater ICCs were 0.712 and 0.811 for NDP, 0.592 and 0.797 for NDT, and 0.575 for FPI. Test-retest ICCs of the SAI and DAI were 0.850 and 0.876, respectively.

Conclusion: Navicular drop is relatively more reliable than other traditional techniques. Also, the FPI-6 has excellent intrarater reliability, but only moderate interrater reliability. The results can provide clinicians and researchers with a reliable way to implement foot posture assessment.

Author keywords: Reproducibility of Results; Foot; Body Weights and Measures; Procedures and Techniques Utilization

Author affiliations: MK: Department of Physiotherapy and Rehabilitation, Faculty of Health Sciences, Izmir Katip Celebi University, Izmir, Turkey, Institute of Health Sciences, Dokuz Eylul University, Izmir, Turkey; MAC: Institute of Health Sciences, Dokuz Eylul University, Izmir, Turkey; AE, IES, SA: School of Physical Therapy and Rehabilitation, Dokuz Eylul University, Izmir, Turkey.

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