Classification of the height and flexibility of the medial longitudinal arch of the foot

Abstract

Background: The risk of developing injuries during standing work may vary between persons with different foot types. High arched and low arched feet, as well as rigid and flexible feet, are considered to have different injury profiles, while those with normal arches may sustain fewer injuries. However, the cut-off values for maximum values (subtalar position during weight-bearing) and range of motion (ROM) values (difference between subtalar neutral and subtalar resting position in a weight-bearing condition) for the medial longitudinal arch (MLA) are largely unknown. The purpose of this study was to identify cut-off values for maximum values and ROM of the MLA of the foot during static tests and to identify factors influencing foot posture.

Methods: The participants consisted of 254 volunteers from Central and Northern Denmark (198 m/56 f; age 39.0 ± 11.7 years; BMI 27.3 ± 4.7 kg/m2). Navicular height (NH), longitudinal arch angle (LAA) and Feiss line (FL) were measured for either the left or the right foot in a subtalar neutral position and subtalar resting position. Maximum values and ROM were calculated for each test. The 95% and 68% prediction intervals were used as cut-off limits. Multiple regression analysis was used to detect influencing factors on foot posture.

Results: The 68% cut-off values for maximum MLA values and MLA ROM for NH were 3.6 to 5.5 cm and 0.6 to 1.8 cm, respectively, without taking into account the influence of other variables. Normal maximum LAA values were between 131 and 152° and normal LAA ROM was between -1 and 13°. Normal maximum FL values were between -2.6 and -1.2 cm and normal FL ROM was between -0.1 and 0.9 cm. Results from the multivariate linear regression revealed an association between foot size with FL, LAA, and navicular drop.

Conclusions: The cut-off values presented in this study can be used to categorize people performing standing work into groups of different foot arch types. The results of this study are important for investigating a possible link between arch height and arch movement and the development of injuries.

Figure 1

Navicular height with the foot in subtalar neutral position. The foot was in the subtalar neutral position and landmark 2 (navicular tuberosity) was used to measure the navicular height and the navicular drop. With the foot in a weightbearing position the measurements were repeated, and navicular tuberosity was marked again.

Figure 2

Longitudinal arch angle with the foot in subtalar neutral position. The foot was in its subtalar neutral position and the landmarks (1-3) were used to measure LAA. 1 head of first metatarsal bone; 2 navicular tuberosity; and 3 centre of the medial malleolus. A line was drawn from landmark 1 to 2 and from landmark 2 to 3. The superior angle between line 1 to 2 and line 2 to 3 was measured in degrees. With the foot in a weightbearing position, the measurements were repeated and the navicular tuberosity was marked again.

Figure 3

Feiss line with the foot in subtalar neutral position. The foot was in its subtalar neutral position and the landmarks (1-3) are used to measure Feiss line. 1 head of first metatarsal bone; 2 navicular tuberosity; and 3 centre of the medial malleolus. A line between landmark 1 and 3 was drawn and the perpendicular distance between landmark 2 and line 1 to 3 was measured. With the foot in a weightbearing position, the measurements were repeated, and the navicular tuberosity was marked again.