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A foot orthosis is a medical device that is designed to alter the way in which forces are applied to the sole of the foot. Foot orthosis/orthoses is the term used by health professionals for these devices, but this term is used interchangeably with insole, shoe insert and footbed.

Changing the forces under the foot may be achieved by altering the geometry (shape) of the insole or the material of the insole. For example, the orthosis may have a raised arch profile to increase the contact between the orthosis and arch of the foot, and distribute forces to an area of the foot not normally bearing load (so called arch support). By changing the material from a rigid leather or plastic to a compliant rubber or silicon gel, the ability of the orthosis to absorb shock and cushion the foot will be increased.

Anatomy of a foot orthosis:

The key features of a foot orthosis are:

•	Medial arch elevation to support the bones on the medial side of the foot (talus, navicular, medial cuneiform, first metatarsal)

•	Lateral arch elevation to support the bones on the lateral side of the foot (calcaneus, cuboid, fifth metatarsal)

•	Heel wedge - used to tilt the heel medially or laterally depending upon the clinical problem the patient presents.

•	Heel raise - used to elevate the back part of the foot and tilt the foot downwards (plantarflexion).

Many health professions use extra orthotic features to address the position or alignment of specific foot bones or redistribute pressure under the foot. For example, a dome shaped elevation is used to increase loading at a specific site, to help separate two metatarsals for example. Or, the opposite, a dome shaped depression, is used to reduce pressure under a site of pain or pathology (such as a corn or callus).

Many health professionals only use the shape of the patients foot to determine the shape of the foot orthosis but technical developments mean that both foot shape and load distribution under the foot when walking can now be combined.

A wide range of materials are used to manufacture foot orthoses. These include different densities of Ethylene-vinyl acetate (EVA), carbon fibre, thermoplastics, poron, plastazote and silicon based materials.

Uses of foot orthoses

Foot orthoses can be used to alter the alignment of the bones in the foot, leg and potentially the spine too. By changing the alignment of the foot the forces and stresses in the associated muscles and ligaments and joints will be altered. For example, by reducing the amount or speed of foot pronation that occurs after the heel hits the ground, the muscles that would otherwise control this motion may have less work to do.

Foot orthoses can also be used to absorb shock (absorb energy) and alter loading under the foot. By the orthotic absorbing force the body receives less or altered energy as it contacts the ground. By using a highly compliant material under the foot, for example, the rate by which forces are applied to the heel may be reduced. By using a highly compliant material under the foot the area over which load is applied may be increased, which will reduce the pressure under some sites of the foot. Foot pressure is strongly related to foot pain.

Foot orthoses are widely used by Podiatrists, Physiotherapists, Physical Therapists, Orthotists and related professions for a very wide range of clinical problems. These include:


 * Heel pain
 * Plantar Fasciitis
 * Anterior Knee Pain (runners knee)
 * Shin splints
 * Achilles injuries
 * Bunion pain
 * Pain under the forefoot (ball of foot)
 * Recurrent ankle sprains
 * Knee arthritis
 * Illio-tibial band syndrome

They are used both to treat these problems once they have occurred but some advocate use of foot orthoses to prevent injury (mainly in athletes and some diseases that can alter foot structure, such as rheumatoid arthritis). They are worn by a large number of sports professionals, by children experiencing specific foot problems , young adults and older people , as well as those with significant foot disease (e.g. diabetes , rheumatoid arthritis ).

Types of foot orthosis:

There are many different types of foot orthoses and there in no agreed terminology to describe them, thus lots of the following terms refer to the same orthoses

Categorised by manufacture process:

Custom made orthoses – made by matching the shape of the foot orthosis to the shape of the sole of the foot when a person is standing or lying. These orthoses are made bespoke for each person. The shape of the foot is captured using a plaster of paris cast, a foam impression box, or laser scanner. How the shape data is interpreted is determined by a trained health care professional or technician.

Pre fabricated orthoses – made to a standard shape predetermined by the manufacturer.

Categorised by purpose:

Functional foot orthosis – designed to alter the alignment of the structures of the foot in order to improve foot motion and position whilst walking and running. This is with a view to reducing the risk of injury or reducing stress in painful structures (such as a tendon or muscle)

Accommodative foot orthoses – these are designed to increase the contact area between the insole and foot so as to reduce pressures under the foot. They do not attempt to alter foot alignment but rather manage the fact that the foot is already is a poor position. This may be due to a foot deformity due to diabetes or arthritic condition.

Total contact orthoses – these are similar in principle to accommodative orthoses as they attempt to manage the distribution of load under the foot rather than realign the foot. They are most commonly used in diabetes where there is known sensory loss and risk of overloading the sole of the foot.

Evidence

There is no definitive evidence to indicate in which clinical conditions foot orthoses work, for which people they work, and how much you need to wear a foot orthosis for them to work. Foot orthoses have multiple complex and concurrent effects on the foot and lower limb and scientists are not able to measure all these effectives accurately (bony alignment, muscle and tendon stress and so on).

The lack of evidence contrasts with the strong belief in the clinical community that foot orthoses are beneficial and many users are advocates. A number of structured reviews of the evidence have been published in order to inform use of foot orthoses in health care contexts and identify mechanisms of action of foot orthoses. ''