Lower limb injuries are a large problem in athletes. However, there is a paucity of knowledge on the relationship between alignment of the medial longitudinal arch (MLA) of the foot and development of such injuries. A reliable and valid test to quantify foot type is needed to be able to investigate the relationship between arch type and injury likelihood. Feiss Line is a valid clinical measure of the MLA. However, no study has investigated the reliability of the test.
The purpose was to describe a modified version of the Feiss Line test and to determine the intra- and inter-tester reliability of this new foot alignment test. To emphasize the purpose of the modified test, the authors have named it The Navicular Position Test.
Intra- and inter-tester reliability were evaluated of The Navicular Position Test with the use of ICC (interclass correlation coefficient) and Bland-Altman limits of agreement on 43 healthy, young, subjects.
Inter-tester mean difference -0.35 degrees [–1.32; 0.62] p = 0.47. Bland-Altman limits of agreement –6.55 to 5.85 degrees, ICC = 0.94. Intra-tester mean difference 0.47 degrees [–0.57; 1.50] p = 0.37. Bland-Altman limits of agreement –6.15 to 7.08 degrees, ICC = 0.91.
The present data support The Navicular Position Test as a reliable test of the navicular bone position during rest and loading measured in a simple test set-up.
The Navicular Position Test was shown to have a high intraday-, intra- and inter-tester reliability. When cut off values to categorize the MLA into planus, rectus, or cavus feet, has been determined and presented, the test could be used in prospective observational studies investigating the role of the arch type on the development of various lower limb injuries.