A prescription foot orthosis is an in-shoe brace which is designed to correct for abnormal foot and lower extremity function thus reducing the strain on injured structures in the foot and lower extremity. Foot orthoses help prevent future problems from occurring in the foot and lower extremity by reducing abnormal or pathological forces acting on the foot and lower extremity.
Podiatrists prescribe two main types of prescription foot orthosis: accommodative orthoses and functional foot orthoses. Both types of prescription foot orthoses are used to correct the foot plant of the patient so that the pain in their foot or lower extremity will improve so that normal activities can be resumed without pain. However, accommodative and functional foot orthoses are generally made using different materials and may not look or feel the same. Both types of prescription foot orthoses are nearly always prescribed as a pair to allow more normal function of both feet.
Accommodative Foot Orthoses
Accommodative foot orthoses are used to cushion, pad or relieve pressure from a painful or injured area on the bottom of the foot. They may also be designed to try to control abnormal function of the foot. Accommodative orthoses may be made of a wide range of materials such as cork, leather, plastic foams, and rubber materials. They are generally more flexible and soft than functional foot orthoses. Accommodative orthoses are fabricated from a three dimensional model of the foot which may be made by taking a plaster mold of the foot, stepping into a box of compressible foam, or scanning the foot with a mechanical or optical scanner.
Functional Foot Orthoses
Functional foot orthoses are used to correct abnormal foot function and, in so doing, also correct for abnormal lower extremity function. Some types of functional foot orthoses may also be designed to accommodate painful areas on the bottoms of the foot, just like accommodative foot orthoses. Functional foot orthoses may be made of flexible, semi-rigid or rigid plastic or graphite materials. They are relatively thin and easily fit into many types of shoes. They are fabricated from a three dimensional model of the foot which may be made by taking a plaster mold of the foot. A prescription is then produced and the orthotics are manufactured.
Functional foot orthoses are useful in the treatment of a very wide range of painful conditions of the foot and lower extremities. Big toe joint and lesser toe joint pain, arch and instep pain, ankle pain and heel pain are commonly treated with functional foot orthoses. Since abnormal foot function causes abnormal leg, knee and hip function, then functional foot orthoses are commonly also used to treat painful tendinitis and bursitis conditions in the ankle, knee and hip, in addition to shin splints in the legs. The advantages of functional foot orthoses are that they are relatively durable, infrequently require adjustments and more likely to fit into standard shoes. The disadvantages are that they are relatively difficult to adjust and relatively firm and less cushiony.
Foot and Lower Extremity Biomechanics
The study of the mechanical nature of the foot and lower extremity is called biomechanics. It is a specialized branch of science that uses the mechanical principles of physics to study the motions and forces on the human body. Understanding the biomechanics of the foot and lower extremity is of critical importance when the mechanism of an injury must be determined to decide on a appropriate treatment plan for the patient.