A close evaluation of the anatomy and structure of the foot reveals three arches that form the plantar vault.1 This architectural design provides substantial strength, while still permitting sufficient flexibility to accommodate changes in terrain, and to provide propulsion. The foot’s arched structure is not present at birth, but develops during childhood, by age 6 or 7 in most people.2 Breakdown in any of these three arches can result in abnormal gait and transmission of asymmetrical forces into the pelvis and spine.
Medial Longitudinal Arch
The most obvious arch is seen along the medial aspect of the foot. The navicular bone forms the “keystone” of this large and long arch, which is supported primarily by the plantar fascia and spring ligament.3 Years ago, John Basmajian, MD, (the “father of electromyography”) demonstrated that the muscles of the foot and lower leg do not provide support for the medial arch, except during toe-off when walking or while standing on tip-toe. He said, “From the present study, one may conclude that, in the standing-at-ease posture, muscle activity is not required and the muscles are inactive.…”4 While he believed, in 1963, that he had settled the controversy regarding active (muscular) versus passive (ligamentous) support for the medial arch, there still remains much misinformation and persisting, misguided attempts at “strengthening muscles to rebuild the arch.”
The most effective method for evaluating the function of the connective tissues that support the medial arch is to perform a comparison between its non-weight bearing and weight bearing alignment. This procedure is called the “Navicular Drop Test”, and was first described by Brody. 5 The easy-to-perform clinical test objectively documents the presence (or absence) of collapse of the medial longitudinal arch, and has been used successfully to evaluate the risk of athletes with ACL ruptures.6
Lateral Longitudinal Arch
This arch is located along the outside of each foot. Because the cuboid bone serves as its structural keystone, the lateral arch relies much less on connective tissues for its support. For this reason, proper function of the lateral arch is very dependent on the alignment of the cuboid, which is frequently found to be in need of adjustment. Proper support for this arch is at least as important as for the other two, but is surprisingly absent in many orthotics.
Anterior Transverse (Metatarsal) Arch
This arch extends from the metatarsal heads back to the tarsal bones, and runs from the medial to the lateral sides of the foot. At its most anterior portion, the metatarsal heads contact the ground. Poor function and loss of this arch will often result in a build-up of thick callus underneath the metatarsal heads. Recurrent “dropped” metatarsal heads and/or irritation of one of the interdigital nerves (a “Morton’s neuroma”) are also good indications that this arch is not being supported properly by the plantar fascia.
Helping the Faulty Vault
The structural design of the three-arched plantar vault is very good at supporting weight and carrying high loads, while remaining flexible. During normal standing, the load of the body is balanced over the center of the foot, anterior to the ankle. This places the greatest amount of load at the apex of the three arches. This force is then distributed along the “buttresses” of the arches to the heel (which bears 50% to 60% of body weight) and the metatarsal heads (which bear 40% to 50% of body weight). Loss of this configuration will result in abnormal force concentrations, which will eventually cause degenerative and symptomatic clinical conditions.
Collapse or dysfunction of any of the arches needs to be addressed with custom-made orthotics that will support the patient’s foot throughout the gait cycle, while controlling the impact forces. Particularly when there is asymmetry between the feet, arch problems can cause abnormal rotational forces to be transmitted into the pelvis and spine, resulting in chronic spinal symptoms. For this reason alone, doctors of chiropractic need to be aware of the status of their patients’ three arches, since they can have a substantial impact on spinal health.
Dr. John J. Danchik is the seventh inductee to the American Chiropractic Association Sports Hall of Fame. He is the current chairperson of the United States Olympic Committee’s Chiropractic Selection Program. He lectures extensively in the United States and abroad on current trends in sports chiropractic and rehabilitation. Dr. Danchik is an associate editor of the Journal of the Neuromusculoskeletal System. He has been in private practice in Massachusetts for 28 years. He can be reached by e-mail at [email protected].
References:
1. Kapandji IA. Physiology of the Joints: Lower Limb (2nd ed.). New York: Churchill Livingstone, 1981:154-182.
2. Gould N, Moreland M, Alvarez R et al. Development of the child’s arch. Foot Ankle 1989; 9:241-245.
3. Huang CK, Kitaoka HB, An K-N, Chao EY. Biomechanical evaluation of longitudinal arch stability. Foot Ankle 1993; 14:353-357.
4. Basmajian JV, Stecko G. The role of muscles in arch support of the foot: an electromyographic study. J Bone Joint Surg 1963; 45A:1184-1190.
5. Brody D. Techniques in the evaluation and treatment of the injured runner. Orthop Clin North Am 1982; 13:541-558.
6. Beckett ME et al. Incidence of hyperpronation in the ACL injured knee: a clinical perspective. J Athl Train 1992; 27:58-62.