William M. Austin, DC, CCSP, CCRD
Director of Professional Education
When a doctor of chiropractic encounters a patient with low back pain, a careful examination of the spine is necessary. Often overlooked, though, is the importance of the feet to the normal function of the lower back. When patients don’t respond as well as expected to their chiropractic care, frequently there is a source of interference found in the pedal foundation. A recent study concluded that “there are small, but important, inter-segmental movements of the spine during gait.”1 An abnormal gait, no matter what the source, will eventually interfere with these important movements, and eventually back pain develops.
The foundation provided by the feet and legs must bear the weight of the entire body (and considerably more during running and other sports). If there is insufficient or inadequate support from the pedal foundation, the spine will be exposed to abnormal stresses and strains that eventually develop into low back pain. Excessive stresses on the spine can be the result of abnormal foot biomechanics, poor function of the foot/ankle complex, excessive shock transmission, or leg length asymmetry. Recognizing and then responding appropriately to these factors separates the doctors of Chiropractic from the spinal technicians.
When some part of the foot is not moving properly (either insufficient or excessive joint motion), the resulting forces produce effects all along the Kinetic Chain. Investigators have found that “Alteration of normal foot mechanics can adversely influence the normal functions of the ankle, knee, hip, and even the back.”2 Following are some examples of common foot problems that have been found to interfere with spinal function.
First MTP Joint. When the metatarsophalangeal joint of the first toe is stiff and doesn’t flex properly, the transition from midstance to toe off is restricted (Fig. 1). Studies have found that this movement limitation (called “functional hallux limitus”) is a “major gait abnormality that causes lumbar stress.”3 The best treatment for this condition is custom-made functional orthotics that support the medial arch and yet still encourage motion at the first MTP joint.
Plantar Fascitis. When a patient complains of “a sharp heel pain that radiates along the bottom of the inside of the foot,” and especially when the pain is worse when getting out of bed in the morning, inflammation of the connective tissue that supports the underside of the foot must be considered.4 This causes a significant problem with comfortable walking, often resulting in a painful limp. An orthotic with a heel spur cut-out will improve gait and lessen the impact of this condition on the pelvis and spine.
Dropped Metatarsal Heads. If there is no anterior arch to the foot, excessive weight-bearing on the metatarsal heads will cause the transition from foot flat to toe-off to be painful. This alters the timing of the gait cycle, resulting in a rushed propulsion phase. The effects are felt in the pelvis and spine, which are not able to move smoothly through the phases of gait. Orthotic support for the metatarsal arch can improve both the local and biomechanics.5
Foot and Ankle Function
The biomechanics of the foot and ankle are complex, and this region must handle repetitive physical forces. There is normally a smooth transition from pronation following heel strike to supination at toe off. However, when there is excessive pronation or fixed supination, gait is affected, and the entire musculoskeletal system is less efficient. In the case of excessive pronation, the entire lower extremity undergoes excessive medial (internal) rotation, which can cause a range of effects on the pelvis, sacroiliac joints, and spine. Custom-made functional orthotics work to restore and support proper foot function.
Whether a foot tends toward hyperpronation or excessive supination, excessive shock may be transmitted into the spinal joints. “A high-arched (cavus) foot with limited range of motion attenuates shock poorly, and a hypermobile flat foot also does poorly on shock attenuation because of its function near the end of the range of motion.”6 In either case, the forces are felt in the joints of the pelvis and spine. In their classic investigation of skeletal transients on heel strike, Light and his colleagues found a significant stress that could be reduced by using viscoelastic heel pads. Regarding the spine, they warned that “while the transients will load the majority of joints primarily in compression, shear stress will predominate in others, such as the spinal facet and sacroiliac joints.”7 This explains the rapid response of lumbosacral and sacroiliac pain to the use of orthotics that contain viscoelastic materials such as Zorbacel® and TechCel™ (Fig. 2).
Leg Length Asymmetry
When there is a discrepancy in the length of the legs (whether anatomical or functional), the pelvis will tilt to one side. This asymmetry will cause vertebral rotation and recurrent subluxation, and possibly even a functional scoliosis (Fig. 3). The correct use of orthotics (occasionally with an added heel lift) can provide substantial correction for structural short legs.
When a good patient exam reveals any of the deficits in the pedal foundation listed above, the astute doctor of Chiropractic will recognize the need for supplementary treatment. This frequently requires the use of custom-fitted orthotics for long-term stabilization. Flexible orthotics made from viscoelastic materials have now been shown to be the most useful approach. As one investigator has commented, “the full rehabilitation of the back patient with chronic back pain, must include reeducation in the optimal use of the spine in walking.”8 Even expertly applied spinal corrections will often be only partially successful until the lower extremity problems are addressed and corrected.
[Captions for illustrations]
Fig. 1. First MTP Joint at Toe Off [“toe off” panel from gait cycle pic]
Fig. 2. FirmFlex Plus® orthotic with Zorbacel® and TechCel™
Fig. 3. Functional short leg, showing pelvic tilt and spinal curvature [PRS Vol. 8 #5, Fig. 2]
1 Sychewska M, Oberg T, Karlsson D. Segmental movements of the spine during treadmill walking with normal speed. Clin Biomech 1999; 14:384-388.
2 Katoh Y et al. Biomechanical analysis of foot function during gait and clinical applications. Clin Orthop Rel Res 1983; 177:23-33.
3 Dannanberg HJ, Guiliano M. Chronic low-back pain and its response to custom-made foot orthoses. J Am Podiatr Med Assoc 1999; 89:109-117.
4 Sousa TA. Differential Diagnosis for the Chiropractor. Gaithersburg: Aspen Pubs., 1997; 354.
5 Hayda R et al. Effect of metatarsal pads and their positioning: a quantitative assessment. Foot Ankle Int 1994; 15:561-566.
6 Subotnick SI. Forces acting on the lower extremity. In: Sports Medicine of the Lower Extremity. New York: Churchill Livingstone, 1989; 189.
7 Light LH, McLellan GE, Klenerman L. Skeletal transients on heel strike in normal walking with different footwear. J Biomech 1980; 13:477-480.
8 Yekutiel MP. The role of vertebral movement in gait: implication for manual therapy. J Man Manip Therap 1994; 2:22-27.