The Biomechanics of Gait

By: Jeffrey D. Olsen, DC

The biomechanics of gait affect not only the lower extremities, but also the rhythmic movements of the entire body. To appreciate this obvious relationship, picture running with your arms folded across your chest or with your chin tucked. Just like restricting these key components of a balanced gait feels awkward, even apparently smaller disruptions along the Kinetic Chain can have detrimental effects on distant body regions.

Understanding the body in locomotion helps explain many of the distortion patterns that we observe in the patient lying on the exam or adjustment table. Furthermore, this forms the basis for our realization that, as soon as a patient stands up from the treatment table and reintroduces the effects of gravity, everything changes. Quite possibly, this is the time when adjustments begin their unraveling, as soon as the foot hits the ground and postural distortions return.

Three Phases of Stance

Figure 1. Three phases of gait

Figure 1. Three phases of gait

Stance phase, that portion of gait when the foot contacts the ground, is divided into three phases (Fig. 1):

  1. Contact (Heel Strike). The first 27% of stance, from heel strike to forefoot loading.
  2. Midstance. The middle 40%, beginning at forefoot loading and ending with heel lift.
  3. Propulsion (Toe Off). The final 33%, initiated with heel lift and concluding at toeing off.

Patterns of Motion

Figure 2. Effects of excessive foot pronation

Figure 2. Effects of excessive foot pronation

Predictable patterns of motion make up the gait cycle. Here is what occurs from the feet up through the spine (Fig. 2):

  1. Heel strike places the foot in a supinated and semi-rigid position, shifting the majority of contact force to the lateral foot. In walking, supination normally reaches 2 and up to 4˚ in running.The continuation of this process moves the foot structures from a high-arched through a more neutral position, against the resistance of the maximally-rigid, temporarily supinated foot. Flattening the arch dissipates energy and provides major shock absorption with each step.
  2. Pronation begins as body weight transfers over the foot. The arch flattens to dissipate shock while the mid-foot joints “unlock,” allowing the foot to adapt to any uneven terrain. Ideally, the amount of healthy pronation should be limited to 8˚ while walking and up to 12˚ while running.2
  3. Midstance prepares the foot for dynamic propulsion at toe off. The foot must recover from pronation by supinating, re-locking the mid-tarsals, and shifting weight back towards the lateral foot. The foot must instantaneously transform from a fluid adapter to a rigid lever. Since both functions are equally important, this highlights why there is not one ideal or “neutral” position that could accommodate the variable demands placed on the feet.
  4. The tibia undergoes considerable rotational movements for a hinge joint. At heel strike, the tibia is externally rotated. During foot pronation, the tibia internally rotates and then returns to a position of external rotation up to and during toe off. Observe the rotational movement of the tibial tuberosity or patella while standing barefoot and simulating the extremes of foot supination and pronation. Limiting excessive rotational strain on the tibia is important for reducing or preventing many common conditions involving the knee.
  5. The spine also reacts to movements in the feet. In a normal resting stance, the spine balances on a level sacral base created by legs of equal length and level femoral heads. During normal gait, this foundation remains fairly level when viewed from the side. When one foot is on the ground, the gluteus maximus on that side contracts, raising the unsupported pelvis slightly above level. This steady motion is made possible by significant lateral displacements of the center of mass found near the pelvic bowel. This shift to the weightbearing side helps maintain body weight centered over the hip. Meanwhile, the weightbearing ilium rotates anterior. Asymmetrical hyperpronation or any other cause of leg length inequality increases time spent in anterior pelvic rotation.

Consequently, the lumbar lordosis is increased, putting excessive pressure on the posterior spinal joints. The patient is not only likely to experience increased facet irritation, but also to compensate with an increase in the thoracic kyphosis and with anterior weightbearing of the cervical spine. In fact, Cailliet says that for an inch of abnormal anterior cervical translation, there is a corresponding ten-fold increase in cervical spine muscle effort.This postural presentation of the classic Chiropractic patient sets the stage for injury, fatigue, and degenerative arthritis.

Postural Distortion

Such far-reaching, complex motions of the gait cycle indicate the extent of stress that can result from interference with the timing, sequence, and necessary rotation of movement. Muscles, as well as joints, are affected by postural distortion and can also work against the provider by resisting efforts to correct joint position. A muscular link between low back pain and the subsequent development of cervical symptoms also supports this chain-theory of reactions throughout the musculoskeletal system.4

Recent emphasis has shifted to balancing activity among groups of muscles for the prevention and management of pain syndromes,since muscle dysfunction can either be a direct source of pain or complicit in pain referral. You will often note a strength difference between agonists and antagonists. Generally trunk extensors are stronger than flexors.6

Furthermore, it is understood that some muscles are prone to weakness and others to tightening when injured. “These muscle reactions are not random but are consistent and it is considered that such typical responses of muscle tightness and weakness occur throughout the whole muscular system.”7

Improperly functioning muscles also affect normal transmission of proprioceptive feedback, another mechanism in the Kinetic Chain relationship. “The importance of adequate sensory input, proprioceptive control and proper function of sensorimotor integration has probably been underestimated in the pathogenesis of low back pain. For this reason, proprioceptive facilitation techniques should be included in the therapeutic programs for those suffering from low back pain syndromes and postural defects.”7

Orthotic Support

Figure 3. Foot Levelers’ Gait Cycle System

Figure 3. Foot Levelers’ Gait Cycle System

Chiropractic adjustments of the spine improve proprioceptive input by normalizing joint alignment and muscle tonus. Furthermore, because the feet contain approximately one quarter of all the body’s joints and, therefore, a concentration of proprioceptive fibers, it becomes logical to conclude that support of the postural foundation using custom-made orthotics will enhance balance and muscle coordination. In fact, this was the conclusion reached during research involving Foot Levelers’ custom orthotics, published in the Journal of Manipulative and Physiological Therapeutics.And Foot Levelers’ orthotics which offer the patent-pending Gait Cycle System™ (Fig. 3) are the most supportive orthotics available today.

It’s advantageous and efficient to keep the center of gravity balanced near the midline and center of the pelvis. Therefore, any distortions in the lower extremity must automatically result in an equal but opposite distortion pattern above the pelvis. In fact it may not always be easy to tell which distortion started first, but it is more important to realize that without correcting both, any correction will only be temporary.

Active Rehabilitation

Figure 4. Foot exercise with THERA-CISER

Figure 4. Foot exercise with THERA-CISER

Did you know that the highest-value CPT codes for therapy procedures include doctor-assisted, patient-active rehabilitation? Insurance providers know the long-term gains and cost savings of active rehabilitation. Once you have stabilized the pedal foundation with orthotics and adjusted the associated distortion patterns, it is essential to retrain the muscular system to help maintain your corrections. Reverse distortion training with variable resistance is all that is necessary (Fig. 4). Foot Levelers’ low-tech THERA-CISER® is inexpensive, the exercises are simple, and the patient feels no pain. For best results, simply have the patient perform an appropriate exercise in the position of function (position in which the distortion pattern was noted).

Conclusion

When patients don’t respond to your Chiropractic care as expected, look for a collapse in the arches of the feet or for habitual posture distortions. Chiropractors are equipped to address the several components of joint subluxation, muscular imbalance, and sensorimotor feedback errors. However, unless treatments are based on a global, top-to-bottom analysis, results will likely be short lived. Successful treatments will combine specific adjustments to counteract the patterns of joint dysfunction, combined with rehabilitation of specific muscle groups and support for deficient structures, including the feet and lower extremities.

References

  1. Christensen KD. The Ankle/Foot. Connective Tissue Reactions. Dubuque, Foot Levelers College Division, 1986.
  2. Kapandji IA. The Physiology of Joints—Vol. 2. New York: Churchill Livingstone; 1970.
  3. Cailliet R. Neck and Arm Pain. Philadelphia: F.A. Davis; 1981.
  4. Horal J. The clinical appearance of low back disorders in the city of Gothenburg, Sweden. Acta Orthop Scand (suppl) 1969; 118:15.
  5. Lewit K: Manipulative Therapy in Rehabilitation of the Motor System. London: Butterworth; 1985.
  6. Langrana NA, Lee CK, Alexander H, Mayott CW: Quantitative assessment of back strength using isokinetic testing. Spine 1984; 9:287.
  7. Jull GA, Janda V. Muscles and motor control in low back pain: assessment and management. In Physical Therapy of the Low Back. New York: Churchill Livingstone; 1987.
  8. Stude DE, Brink DK. Effects of nine holes of simulated golf and orthotic intervention on balance and proprioception in experienced golfers. J Manip Physiol Ther 1997; 20:590-601.