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lacing design and tightness, and the material of the shoe upper will all
influence the movement of the foot in the shoe. The uppers and lacing
apply a compression force against the dorsum of the foot, in effect holding
the foot down against the sole of the shoe. The lateral aspect of the upper
will be stretched by pronation of the foot and can thus resist pronation if
it is stiff enough and if the lacing creates sufficient compressive forces
against the foot. The upper material on the medial side experiences
compression, but may resist the foot movement if it is sufficiently stiff,
particularly if there is some medial arch support built in. If the shoe is
made with too much material on the lateral and medial sides of the foot
then it will be ineffective in controlling foot motion inside the shoe. In the
area of the medial arch, the width of the sole at the site of the navicular
can influence the angle at which the shoe upper contacts the arch of
the foot.
The stiffness of the material is a key feature of any ability to resist foot
motion. The stiffener used in the heel counter will resist heel eversion if it
extends sufficiently on the medial and lateral sides of the heel. The shank
between the heel and forefoot will help prevent midfoot motion since this
relies on dorsiflexion of the shoe in this midfoot area. It will also help resist
frontal plane twisting of the shoe, another component of pronation of the
foot. Sole stiffness will also resist the stretching of the sole created by
sole dorsiflexion, and thus resist midfoot dorsiflexion.
As well as using wedge material on a foot orthosis to control pronation
of the foot, the materials of the sole can also be used to influence foot
motion. Wedges can be incorporated into the sole unit themselves, or
materials of different stiffness can be used on the medial and lateral sides
of the heel. Using a stiffer material on the medial side will help increase
inversion moments acting on the heel, and thus help resist eversion of
the heel - a component of pronation. The use of mixed materials in the
sole unit is one of the key features of running footwear that purports
to 'control pronation of the foot'. This footwear often has an insert on
the medial side of the shoe that is higher density than the rest of the
sole unit.
Footwear suitability assessment tools
In relation to the it of the footwear, there are assessment tools that help
the patient and the practitioner to evaluate it and suitability. Footwear
assessment practices tend to be subjective and to focus on the style of
the footwear rather than the suitability of the footwear for the individual
patient and their presenting foot problems. Non-specialist footwear
assessment relies on length and sometimes width and heel to ball meas-
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