Stance affects musculoskeletal integrity because it creates a closed kinetic chain among the body's four main support systems: the feet, pelvis, torso, and cervical region.Forces are transmitted between the "links" of this chain in such a way that pathologies in one region can instigate problems elsewhere. Gravitational forces and heel strike shock from walking are two examples of ordinary forces which affect the kinetic chain.
Weightbearing stance also creates load or stress that precipitates soft-tissue deformation. Over time, unchecked stress due to imbalance or structural abnormalities can create plastic deformation and laxity in connective tissue. An example is "fallen arches," the loss of support in pedal tissues due to the repeated stress of normal pronation.2
The effects of weightbearing stance have been shown in a study of scoliosis patients involving a comparison of standing and recumbent x-rays. Weightbearing increased the degree of lumbar curves and changed postural and biomechanical vertebral patterns.3 Another group of subjects free from relevant biomechanical abnormalities recorded calcaneal eversion or subtalar pronation significantly greater in stance than during passive calcaneal eversion maneuvers.4
The Pedal Foundation
Weightbearing force is a significant factor in the structure and function of the feet, which are the foundation of human posture. The weightbearing position exposes the lower extremities to the greatest levels of stress; also, more problems appear than in a non-weightbearing posture.5
The foot serves to support and move the body, and to absorb ground reaction forces during locomotion. The integrity of its many functions depends largely on the plantar vault, formed by the longitudinal, medial and transverse arches.6 Weakness in one or more of these arches can have pathological consequences throughout the body.
The continued strain of standing and walking can stress pedal tissue to the point of plastic deformation. Laxity destroys motion control, leading to abnormal alignment and kinetic response. Excessive pronation, cited earlier as a factor in functional LLI, is the most common form of hypermobility and a contributor to more chronic posture problems than any other foot disorder.7
The effects of excessive pronation can be traced along the extremities up to the spinal-pelvic complex. Abnormal inward rotation of the tibia and femur threaten the knee and can instigate inward hip rotation. The body is also at increased risk of pathological shock due to plastic deformation, with symptoms such as osteoarthritis, tendinitis, and slow or incomplete recovery of other musculoskeletal conditions.7
Custom-made, flexible orthotics that control the degree and duration of pronation can alleviate these symptoms related to pedal imbalance.8 Orthotics improve support and alignment to enhance body structure and function9 and modify minor deficits that inhibit the integrity of the pedal foundation.8
A weightbearing casting method will provide the most accurate picture of pedal imbalance and dysfunction for prescribing orthotic correction. As Yochum has written, "Use of a weightbearing casting method to obtain quantifiable information on the extent of pedal imbalance is recommended."10 In a non-weightbearing "neutral" position, even a flattened arch will exhibit a deceptive integrity. When casts are taken with the foot in the position of function, areas of weakness are easier to detect.
Detecting Postural Distortions
A range of conditions, including disc degeneration, myofascial pain syndromes and chronic strains can be attributed to the broad category of musculoskeletal dysfunctions described as "postural abnormalities."11 The traditional methodology for clinical evaluation of posture requires the body to be in a standing, weightbearing position.
The ideal efficient posture is maintained with only minimal muscular effort and is the result of sound skeletal structure, soft tissue integrity and neurological control. Optimal balance of the spine's normal physiological curves contributes to healthy posture.
Structural imbalances or weakness in soft tissues may be difficult to detect, especially those which have developed insidiously in response to factors such as pedal imbalance. When the body is viewed as a closed kinetic chain (created by weightbearing), underlying causes of nonspecific pain can be more readily identified.
Visual postural analysis is a matter of comparison between the areas detailed in Table 1 below.
Table 1: Visual postural analysis.
|Cervical||Skull and cervical spine in relation to torso mass.|
|Torso||Shoulders, rib cage and thoracolumbar spine in relation to pelvis.|
|Pelvis||Pelvic mass in relation to feet at midpoint between ankles.|
|Feet||Ankles, calcanei, arches and metatarsals in relation to ground surface and to each other.|
Correction of postural distortions will involve any of several modalities depending on the extent and etiology of dysfunction. Specific chiropractic adjustments that improve alignment and mobility and that reduce fixations may be adequate for short-term problems. The goal is to normalize range of motion and encourage a midpoint rest position for involved joints.
Rehabilitative exercise to improve soft tissue integrity is helpful for longer-term abnormalities or to retrain weakened muscular support systems. Mirror image correction exercises allow patients to perform very posture-specific asymmetric exercise maneuvers against resistance.12 This helps stretch shortened connective tissues while strengthening and retraining imbalanced support mechanisms.
- Wu KK. Foot Orthoses: Principles and Clinical Applications. Baltimore: Williams & Wilkins, 1990.
- Blake RL, Ferguson H. Foot orthoses for severe flatfoot in sports. J Am Pod Med Assoc 1991;81(10):549-555.
- Friberg O. Statics of postural pelvic tilt scoliosis: radiographic study on 288 consecutive chronic lbp patients. Clin Biomech 1987;2(4):211-219.
- Lattanza L. Closed versus open kinetic chain measurements of subtalar joint eversion: implications in clinical practice. J Orthop Sports Phys 1988;9:310-314.
- Hoppenfeld S. Physical Examination of Spine and Extremities. Norwalk: Appleton Century Crofts, 1976.
- Kapandji IA. Physiology of Joints, Vol. 2: Lower Limb, 5th Ed. New York: Churchill Livingstone, 1987.
- Root ML. Clinical Biomechanics II: Normal and Abnormal Function of the Foot. Los Angeles: Clinical Biomechanics Corp., 1977.
- Christensen KD. Orthotics: do they really help a chiropractic patient? ACA J of Chiro 1990;27(4):63-71.
- Lening PC. Weightbearing casting and orthotics. Digest Chiro Econ 1992;34(5):52.
- Yochum TR, Rowe LJ, Barry MS. Natural history of spondylosis and spondylolisthesis. In: Essentials of Skeletal Radiology, 2nd ed. Baltimore: Williams & Wilkins, 1996;364.
- Reilly B. Practical Strategies in Outpatient Medicine. Philadelphia: WB Saunders Co., 1984.
- Harrison DD (ed.) Spinal Biomechanics: A Chiropractic Perspective. Harrison Pubs., 1992:58.
Kim Christensen, DC, DACRB, CCSP
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