From the ground up

Understanding when your patients need biomechanical support during the gait cycle.

During the act of walking, the lower extremities interplay with the spine. A normal gait creates repetitive motions from the feet to the lower extremities, to the pelvis and spine, up to the head. As a smooth symmetrical gait is associated with proper vertebral function, likewise abnormalities in one or both feet can cause spinal subluxations to develop and recur.^1,2

Problems with gait

Problems with walking can be caused by a number of neuromuscular conditions and biomechanical abnormalities. Neuromuscular conditions include ataxic gait (due to cerebellar or sensory problems), Parkinsonian gait (shuffling and festination), Trendelenburg gait (due to weakness of the gluteus medius muscle), steppage gait (caused by foot drop), or hemiparetic gait (with circumduction due to partial paralysis).³ These conditions require extensive evaluation and testing but are rarely seen in clinical practice.

Biomechanical abnormalities are more common, and are frequently the source of persistent symptoms seen in chiropractic patients. Whenever there is a chronic or persistent subluxation complex, a search for underlying factors must include the feet and lower extremities.

Gait cycle components

Bipedal walking consists of two phases for each lower extremity—the swing phase, when the foot is off the ground, and the stance phase, when the foot is on the ground and bearing weight.

During normal walking, at one point both lower extremities bear weight (one is finishing toe-off and the other is starting heel strike). This is called double support. When running, there is an instant during which there is no contact with the ground—the runner is briefly flying through the air between phases, and then lands on one foot.

Swing phase

After push-off, the free leg swings through the air for about 40 percent of the gait cycle.⁴ The pelvis rotates forward and the hip flexes, accelerating the leg forward. Muscles contract concentrically to pull the body forward. The knee and ankle flex to clear the ground, and then extend to prepare for the impact of touchdown.

While the swing phase is not usually symptomatic, it may be associated with gait abnormalities due to loss of neurological coordination or muscular weakness.

Stance phase

Once the foot touches down, the leg begins to bear the weight of the body. The stance phase is the most important portion of the gait cycle, as this is when the foot becomes fixed to the ground. It is also the longest phase, at 60 percent. The leg now bears the full weight of the body and supports the pelvis and spine.

It is during the stance part of gait, when the spine is supported on a single leg, that the biomechanics of the foot can interfere with chiropractic care. The three components of the stance phase are: heel strike (touchdown), foot flat (midstance), and toe-off (propulsion).

Heel strike

As the heel contacts the ground, the calcaneus is inverted and the foot is supinated. The ground reaction force is transmitted into the foot at the heel pad, and then the ankle joint absorbs some of the impact. The muscles in the lower leg, primarily the anterior and posterior tibialis muscles, contract eccentrically to slow down the plantar flexion of the foot. When overloaded, these muscles can become painful, causing “shin splints.”⁵

Legs, pelvis, and spine

The force of heel strike transmits a shock wave up the leg to the pelvis, the spine, and into the skull. An experiment with human volunteers found that normal walking produces around 5 Gs of force on the foot and ankle, and a shock wave travels rapidly up the spine.

Within 10 milliseconds of heel strike (faster than conscious response), the scientists recorded a 0.5 G impact at the skull.² Running multiplies the impact of heel strike on the body by about three times (the rule of three).⁶ This is a significant concern for patients who cannot tolerate this level of force, in particular those with degenerative changes in the joints of the lower extremities and the spine.

Biomechanical support

If a patient has shin splints, heel pain, or significant knee or spinal joint degeneration, additional shock absorption can be supplied by orthotic prescription. Several studies have found that the use of a viscoelastic polymer heel cup to reduce heel strike shock will significantly decrease both foot and back symptoms.^7,8

Foot flat

As the foot contacts the ground, it must adapt to a variety of surfaces. From heel strike to foot flat, the foot undergoes a complex rolling inwards, primarily at the subtalar joint.

Pronation accommodates to variable ground surfaces and helps absorb the shock of the entire bodyweight.

Pronation causes a depression of the medial longitudinal arch of the foot, which is sustained by the elastic plantar fascia. If this connective tissue has undergone plastic deformation, it will no longer spring back and the foot stays pronated. When the foot goes too far into pronation, or stays in this position for too long, it won’t progress smoothly into the next phase. Excessive pronation is commonly associated with many foot symptoms.⁶

Excessive pronation

As the foot pronates during the stance phase of gait, there is a normal inward (medial) rotation of the entire leg into the pelvis. In persons with excessive or prolonged pronation, this twisting movement is accentuated.

The increased rotational forces are transmitted up the leg into the pelvis, and especially the sacroiliac joint.⁵ In response, various compensatory pelvic subluxation complexes can develop.

These include pelvic tilt (usually anterior or to one side), innominate rotation (usually postero-inferior), and other complicated adaptations.

The loss of arch height that occurs with excessive pronation allows the pelvis to drop to the more pronated side during stance and gait.⁵ The resulting pelvic tilt lowers the sacral base and drops the lowest freely moveable vertebra. A lateral curvature can then develop in response to the lack of solid support for the base of the spine.

Biomechanical imbalances associated with leg asymmetry and pelvic tilt transmit abnormal forces and sustained stresses to the spinal joints, resulting in classical patterns of microtrauma, cartilage wear, and osteophytes.⁵

Pronation support

Pronation problems require support for the arches of the foot—primarily the medial longitudinal arch (navicular), but also the lateral (cuboid) and the anterior (metatarsal) arches. This relieves stress on the supportive connective tissues and the plantar fascia in particular.

Especially in heavier or more strenuously active patients, additional torsional rigidity must be supplied to prevent medial collapse. In some cases, a special support for the heel prevents excessive eversion—the pronation correction or “varus/valgus wedge” is added under the medial aspect of the calcaneus.

Toe-off

The final aspect of the stance phase starts with heel lift, which progresses to toe-off and provides the propulsion needed to move into the next phase. Biomechanically, the foot goes into supination, becoming a rigid lever. This is aided by extension (dorsiflexion) of the metatarsophalangeal joints and tightening of the plantar fascia (the “windlass effect”). When the plantar fascia is weakened or the first metatarsophalangeal joint is stiff, the foot can’t push off well and tends to roll medially.

This causes the foot to flare outward and leads to symptoms at the first toe, such as hallux valgus or osteoarthritis.

At toe-off, the leg rotates externally and the pelvis moves posterior. Walking with an abnormal gait and poor toe-off causes back pain that can be treated with functional orthotics.³ Poor propulsion adds to the effort required for doing simple activities, and increases oxygen consumption during normal walking.⁶ Sports performance can be hampered significantly.

Metatarsal support

At toe-off, the foot needs to be guided into supination and encouraged to flex at the metatarsal break. This requires a functional orthotic that is flexible at the first metatarsophalangeal junction, yet provides support to the medial foot and first two toes. A connected system

While the feet seem far from the spine, they are intimately connected to it.

Both structural and neurological factors demonstrate this interrelated and integrated system. Posture, balance, coordination, and efficient musculoskeletal function all depend on a smooth gait during normal activity. It is important to investigate the functioning of this interconnection between the feet and the spine.

By providing proper support for each phase of the gait cycle, you can ensure balanced function throughout the musculoskeletal system.

 

Mark Charrette, DC, is a 1980 summa cum laude graduate of Palmer College of Chiropractic. He is a frequent guest speaker at chiropractic colleges worldwide and has taught more than 1,400 seminars worldwide on extremity adjusting, biomechanics, and spinal adjusting techniques. He can be reached at drmarkcharrette@gmail.com.

 

References

¹ Aota Y, Iizuka H, Ishige Y, et al. Effectiveness of a lumbar support continuous passive motion device in the prevention of low back pain during prolonged sitting. Spine. 2007;32(23):E674-7.

² Boswell MV, Shah RV, Everett CR, et al. Interventional techniques in the management of chronic spinal pain: evidence-based practice guidelines. Pain Physician. 2005;8(1):1-47.

³ Yekutiel MP. The role of vertebral movement in gait: implications for manual therapy. J Man Manip Ther. 1994;2:22-7.

⁴ Light LH, McLellan GE, Klenerman L. Skeletal transients on heel strike in normal walking with different footwear. J Biomech. 1980;13:477-80.

⁵ Dananberg HJ, Giuliani M. Chronic low-back pain and its response to custom-made foot orthoses. J Am Podiatr Med Assoc. 1999;89:109-17.

⁶ Subotnick SI. (1989). “Forces Acting on the Lower Extremity.” In: Sports Medicine of the Lower Extremity. New York: Churchill Livingstone:189.

⁷ Faunø P, Kalund S, Andreasen I, Jorgensen U. Soreness in lower extremities and back is reduced by use of shock absorbing heel inserts. Int J Sports Med. 1993;14:288-290.

⁸ MacLellan GE, Vyvyan B. Management of pain beneath the heel and Achilles tendonitis with heel inserts. Brit J Sports Med. 1981;15:117-121.