Reliability of different clinical techniques for assessing foot posture

Key points

1. 01Navicular drop was the most reliable technique overall, with excellent within-rater reliability.
2. 02The Foot Posture Index-6 had excellent within-rater reliability but only moderate between-rater reliability.
3. 03Navicular drift was the least reliable measure tested.
4. 04The static and dynamic arch indices from pedobarography showed good test-retest reliability.
5. 05Averaging 3 repeated measurements raised reliability compared with using a single first measurement.

How it was conducted

Design

Reliability study (intrarater, interrater, and test-retest)

Participants

60 healthy adults aged 18 to 40 years; first 30 also assessed for interrater reliability

Measures tested

Navicular drop (NDP), navicular drift (NDT), Foot Posture Index-6 (FPI-6), static arch index (SAI), dynamic arch index (DAI)

Procedure

Dominant foot only; NDP, NDT, SAI, DAI repeated 3 times; intrarater and test-retest reassessed after 5 days; 2 raters for interrater

Primary outcome

Intraclass correlation coefficients (ICC) and standard error of measurement

What they found

• Intrarater ICC for NDP was 0.934 (first measurement) and 0.970 (average).
• Intrarater ICC for NDT was 0.724 (first measurement) and 0.859 (average).
• Intrarater ICC for FPI-6 total score was 0.945.
• Interrater ICC for NDP was 0.712 (first measurement) and 0.811 (average).
• Interrater ICC for NDT was 0.592 (first measurement) and 0.797 (average).
• Interrater ICC for FPI-6 total score was 0.575.
• Test-retest ICC was 0.805 for SAI and 0.876 for DAI.

Limitations

• Only the first 30 of 60 participants were assessed for interrater reliability because the second rater dropped out for health reasons.
• Results cannot be generalized to people with foot pain or an ongoing foot injury, as only healthy adults were studied.
• Only the dominant foot was assessed, and the sample was a narrow age range (18 to 40 years).

Why it matters

For patients

The foot posture measurement your clinician takes is likely to be consistent if the same person repeats it, which supports tracking changes over time.

For clinicians

Prefer navicular drop and average 3 repeated measurements after a practice session; expect weaker agreement when a different examiner takes over, especially for the FPI-6 and navicular drift.

For readers

This study supports navicular drop as the most reliable bedside foot posture measure but flags that between-examiner agreement is only moderate for most techniques.