The support, protection, propulsion, and balance features of the foot are an important consideration in the delivery of wellness-based chiropractic care

In chiropractic practice, there are bridges constantly being crossed that span the gaps in patients’ belief about their health and wellness. But none is as important as the bridge of confidence and trust, which forms the foundation for all healing and progress. Patients must begin to accept a new way of looking at their ability to be well and stay well.

The uniqueness of the chiropractic model is based on its philosophy that links the balance of structure with the intimate working dynamics of the central nervous system. This is the concept of the vertebral subluxation, which can be viewed as a spinal event that impacts the communication of vital information designed to regulate, animate, and control all function.

The first bridge that is used when observing structural tone and dynamics is the arch system of the foot. This must have the combined dimensions of support, protection, propulsion, and balance. The biomechanics of the foot and ankle and entire kinetic chain are an amazing combination of form and function.

The engineering dilemma of form versus function is like the choice between the chicken and the egg. Does form dictate function, or does function influence form? The chiropractic model realizes that both structural tone and functional tone are absolutely necessary for optimal expression of health. The form of the foot and ankle must match their function. The biomechanical considerations of support, protection, propulsion, and balance will be discussed in relation to the two dimensions of tone.

Form and Function
Support. The entire weight of the body is transferred through point loads during standing posture and during the gait cycle. The engineering of the arch and foot must be stable and flexible to distribute these loads and to minimize damage. The foot is designed with three connected arches that can be viewed as a trampoline along the bottom of the foot. The medial longitudinal arch is sprung from the forefoot to the rearfoot. The spring ligament, or plantar fascia, is a taut fibroelastic band designed to compress as shock and gravity act upon it. Much like the leaf spring in a car, this is a durable, layered structure. Its flexibility and support are derived as much from its shape as from its structural components.

In its ideal position and makeup, the plantar fascia is activated at heel strike, stretches in a uniform way to resist unusual torsional deflections, and then develops kinetic energy along its length. This springing action absorbs axial compressive forces, and, when forward movement vectors are applied, it snaps to a closed position, providing propulsion through its dynamic arc.

The support feature of the plantar fascia is altered as the shape of the foot changes. The rearfoot is most commonly observed to have altered in its position and motion when compared with the forefoot. Excessive pronation of the calcaneus creates a rolling inward and an apparent collapse of the longitudinal arch. As the plantar fascia is constantly overstretched, it gradually thickens and loses its elasticity. Fibrous tissue replaces the elastic nature of the ligament, and eventually mineralization of the attachments can be seen.

Calcaneal spurs are commonly observed in patients with excessive pronation of the calcaneus along with overstretching of the plantar fascia. Centralized and anteromedial heel pain can be elicited with palpation of this spring ligament.

As the flattening of the medial arch occurs, the other arches of the foot are altered. The dynamic trampoline effect is lost as the lateral longitudinal arch and metatarsal arch continue to compensate. The entire foot begins to warp as these support springs are shifted in their alignment. Now, axial compressive forces are deflected improperly and the foot begins to bang down at heel strike and toe-off. What was originally designed to be the first absorptive link of the kinetic chain is now compromised. This sets off a chain reaction as other structures begin to alter and lose their biomechanical advantage.

Protection. The loss of normal force transfer through the foot affects the subtalar joint function. This versatile joint is designed to compensate for uneven ground while positioning the talus for maximal propulsion. With overpronation, the talus sags medially and locks the subtalar joint. The ligaments that hold the talar mortice can become overstretched, leading to inappropriate alignment and allowing forces to transfer through the ankle joint.

In time, the entire kinetic chain can be altered with medial bowing and rotation of the tibia, altered Q-angles, and fixated pelvic ring motion and posture. The unnatural alignment of the foot joints and bones can create a cascading effect along the entire lower-limb kinetic chain. Overpronation of the foot and ankle is commonly seen in dysfunctional pelvic and lower-back pain patterns.

Propulsion. The biomechanical advantage of the foot is found in its ability to support, guide, and provide motion. As heel strike is initiated, the weight of the entire body crosses over the center of gravity, and the foot is pulled forward. As that action occurs, the trampoline action of the three arches is activated. The stretching of these arches creates a concentration of kinetic forces, which snaps back as the body weight passes forward. This ligamentous push aids in the propulsion of the entire body as the gait cycle proceeds.

With overstretching of the plantar fascia, altered alignment of foot bones, and fixated or hypermobile joints, the propulsive features of the foot are diminished. One can imagine how inefficient and tiring the simple act of walking can become when this propulsion feature is altered.

Balance. Posture is a complex neurological event that is observed both locally and globally. The entire posture of a person depends on the ability of the foot to feel the ground and signal the neurological pathways. The foot becomes a sensory plug in the complex array of neural activity that results in dynamic posture. When the position and motion of the foot are altered, the sensory input changes. An endless cycle of change can begin as the biomechanics of the foot deteriorate.

As more collapse occurs, greater forces are absorbed during heel strike, midstance, and toe-off. In turn, the noxious proprioception is detected, and more reactive guarding is applied. The gait cycle begins to falter, and the inefficiencies in the systems are seen in the breakdown of structures of the kinetic chain along with the inefficiencies in neural integration. Surface electromyographic studies can show the dysponetic effect of altered foot posture and neural output in certain postures. This excessive toil and exertion can have a global effect on energy allocation and fatigue. The altered input to the central neural processing affects the ease with which the body adapts to its environment. This shows up as exhaustion and local injury patterns.

Solutions for Your Patients
The biomechanical foot plays an integral role in the structural and functional tone of each patient. An obvious component of a chiropractic evaluation is to assess the relation of the foot to the vertebral subluxation. Looking for alignment discrepancies, fixations within joint complexes, and altered kinetic chain consequences can easily be added into the evaluation protocols.

When patients need pedal support and postural correction, a properly cast, custom orthotic is an excellent choice. These flexible tools can unpack the dysfunctional mechanics and restore better balance to the entire kinetic chain.¹ The application of an orthotic can be viewed as both health promotion and protection. Patients regularly comment on the benefits of orthotic use that go far beyond foot care. Proper foot biomechanics lead to enhanced spinal pelvic stabilization.

Also, the retraining of the neural integration before and after orthotic placement is essential. Chiropractic adjustments intended to restore neural tone and affect structural balance are the natural choice when following the chiropractic paradigm.

Patients view the chiropractic experience as a gateway to natural health and well-being. By applying the principles of form and function to the foot’s gait cycle system and the spine together, a more complete program of care can be monitored. CP

David S. Fletcher, DC, FCCSS (C), a fellow of the College of Chiropractic Sport Sciences (Canada), has been in private practice for 22 years at The Fletcher Clinic, Pickering, Toronto, Canada. He is recognized internationally for blending traditional chiropractic principles with contemporary technologies and strategies. Fletcher can be reached at (905) 831-9696; fletch5@rogers.com;   www.chiroacademy.com.  

Reference
1. Stude DE, Brink DK. Effects of nine holes of simulated golf and orthotics intervention on balance and proprioception in experienced golfers. J Manip Physiol Ther. 1997;20(9):590–601.