Foundations of the Chiropractic Model

We have now seen a wealth of studies demonstrating that spinal manipulation is effective, but it is quite another matter to fully understand how and why. The search for an explanation has absorbed the attention of chiropractors since D.D. Palmer founded the profession in 1895.
The history of chiropractic, like all healing arts, is largely one in which empirical process has preceded theoretical formulation. In other words, from the earliest days practitioners have applied new manual treatment methods on an intuitive, empirical basis, noted that some are more effective than others, and theorized on the basis of these findings as to the underlying mechanisms.

When certain methods have demonstrated their effectiveness over a period of time, they, along with the theories used to explain them, become part of what we might call the “chiropractic corpus,” the body of tradition, evidence, and practice which is the contribution of the chiropractic school of knowledge to the healing arts as a whole.

Not until the late Twentieth Century was this accumulated body of chiropractic knowledge sufficiently grounded in scientific research to allow wide recognition across professional boundaries. Fortunately, that point has now been reached. It therefore seems timely to review the nature of the chiropractic diagnostic and therapeutic model, so that it can be well understood by the public and other health professionals.

Part of this review is an examination of chiropractic theory past and present. It is important to sift out ideas which may have been state of the art in 1910 or 1950, but which are no longer fully tenable. Chief among these is the idea that the chiropractic adjustment works primarily by physically moving a vertebra that is out of place back into place.

The Bone-Out-of-Place Theory

The early chiropractors assumed that their adjustments worked by moving misaligned vertebrae back into line, thereby relieving pressure caused when those bones impinged directly on spinal nerves. The standard explanation given to patients was the analogy of stepping on a garden hose if you step on the hose the water canât get through, and then if you lift your foot off the hose, the free flow of water is restored. Similarly, the explanation went, the chiropractic adjustment removes the pressure of bone on nerve, thus allowing free flow of nerve impulses.

Based on the information available in the early years, such a theory was plausible. Chiropractors were able to feel interruptions in the symmetry of the spinal column with their well-trained hands, and in many cases could verify this on x-ray (discovered in 1895, the same year as chiropractic). They would then adjust the vertebra with manual pressure, attempting to move it back into line. More often than not, patients reported significant functional improvements and healing effects.

But there are problems with the theory. This can most simply and directly be illustrated by noting the fact that, after an adjustment resulting in dramatic relief from headaches or sciatica, an x-ray will rarely show any discernible change in alignment. (Such comparative x-rays are now considered inappropriate, because of the unnecessary radiation exposure). Long-term positive health changes have not been definitively shown to correlate with symmetrical alignment of spinal bones on any consistent basis.

Though much excellent work has been done by chiropractors whose understanding of their healing art was based on the bone-out-of-place theory, the theory has not stood the test of time. This does not mean that chiropractic is invalid, only that this late nineteenth century explanation has been overtaken by later developments.

While misalignments may play a role in the interpretation of spinal subluxations, they are no longer believed to play the central role. But if the old explanation of misaligned bones pressing on nerves is inadequate, what new theory has replaced it? To answer this question, we need to move beyond the essentially two-dimensional viewpoint of the misalignment theory, and include motion as an added dimension.

The Intervertebral Motion Theory

In the 1930s, Belgian chiropractor Henri Gillet developed a theory of intervertebral motion and fixation, in which he asserted that it was loss of normal spinal joint movement, rather than misalignment, that was the underlying explanation for the vertebral subluxation. He agreed with the bone-out-of-place adherents that the interplay between the skeletal system and the nervous system was crucial, but parted ways with them regarding the causal process underlying the abnormal nerve signaling. Rather than attributing the subluxationâs effects to direct pressure of misaligned bone on nerve, Gillet theorized that loss of proper joint dynamics was the underlying issue.

Later work by medical researchers Schmorl and Junghans, and many more who followed, verified the complex role of the “vertebral motor unit,” consisting of bones, muscles, ligaments, blood vessels, and nerves. This model is now widely accepted.

All of these structural components are involved in the subluxation complex. Bypassing the old argument of whether the causative factor in the vertebral subluxation is the bone or the muscle, the work of Gillet, Schmorl, Junghans, and others allowed the problem to be seen from a broader, multi-faceted perspective, in which all components of the intervertebral joint are involved in an elaborate interplay. This model first achieved profession-wide attention among chiropractors in the 1980s, and now enjoys broad acceptance in chiropractic college curricula throughout the world.[1]

Jerome McAndrews, D.C., an early advocate of motion theory and practice who later served as president of Palmer College of Chiropractic, translated this model into visual terms when I spoke with him during preparation of this book.

“View it as a mobile hanging from the ceiling,” Dr. McAndrews said. “As it hangs there, it is in a state of dynamic equilibrium. Then, if you cut one of the strings, the whole mobile starts moving, because its balance has been upset. Eventually, it slows down and reaches a new state of dynamic equilibrium.”

The bodyâs musculoskeletal system works in much the same way, Dr. McAndrews explained. If its normal balance is disrupted, it has no choice but to compensate. Structural patterns will be altered to a greater or lesser degree, depending on the nature and intensity of the forces that threw off the old pattern of balance.

If chiropractic care is sought early, relatively little treatment may be required, because these compensations will not have had time to deeply imbed themselves structurally. Thus, a child injured playing football at age ten might need just one or two adjustments, but if that child waits until age forty before seeking chiropractic care (not an uncommon occurrence), the situation may prove far more complex. Patterns of long-term muscular rigidity, calcium deposits in ligaments, and significant structural shifts of the vertebral column or ribcage, for example, may set in with relative permanence.

In some such circumstances, when much time has passed, the achievable therapeutic goal may be limited to partial restoration of mobility and function. Returning to the once-upon-a-time perfection of the ten-year oldâs pre-injury body becomes impossible somewhere along the way.
The theory of dynamic equilibrium, with its emphasis on intervertebral motion and fixation, has the great advantage of allowing, for the first time, a coherent explanation of chiropractic and the subluxation complex that can be communicated in familiar terms to medical practitioners and researchers. This has resulted in clearer lines of communication between chiropractors and medical professionals. While some hold onto the old model and terminology, the stage has been set for completion of this significant shift in perspective, as the new generation of chiropractic and medical practitioners trained after it took hold comes of age.

Wide-Ranging Effects of Spinal Manipulation

Restoring mobility to a joint by manipulation eases the stress at that joint and in the surrounding tissues. Unless complicating factors are present, muscular tension eases in the area that has been adjusted. As joint dysfunction decreases, other secondary symptoms such as pain, tingling, or numbness along the path of the nerves originating at the involved spinal level also improve.

Though the vast majority of chiropractic patients arrive seeking help for musculoskeletal problems like back pain, neck pain, and headaches, spinal adjustments can also have positive effects on other organs and systems. While chiropractic adjustments are directed to restoring motion at specific vertebral joints, the effects of these adjustments extend beyond the local area where the adjustive force is applied. Effects can extend to all structures served by the nerves originating in the spine.

Thus, neck adjustments can affect not only the neck and arms, but also the function of various organs in the head (via sympathetic pathways), and in the chest and upper abdomen (via the parasympathetic vagus nerve). Upper back adjustments can affect not only the upper back, but also the lungs, heart, and parts of the digestive tract. Adjustments of the lower back may influence not only the lower back and legs, but also the kidneys, pelvic organs and lower digestive tract.

The First Chiropractic Adjustment: A Case of Hearing Restored

The first chiropractic adjustment in 1895 was one in which the patient sought help for back pain, and got results far beyond his expectations. Harvey Lillard, a deaf janitor in the building where D.D. Palmer had an office, came to Palmer bent over with back pain. Palmer gave him a spinal adjustment, after which Mr. Lillard stood up straight, was free of back pain, and able to hear for the first time in many years.

At first, it appeared that Palmer might have discovered a cure for deafness, but similar results were not forthcoming when other deaf people heard about Harvey Lillard and sought Palmerâs help. And while there have been other instances through the years of hearing restored through spinal manipulation (including one by Canadian orthopedist J.F. Bourdillion, M.D.)[2] these have been rare, and no predictable pattern has emerged. The story of Lillardâs recovery has been used for many years to disparage chiropractic, with repeated charges by the naysayers (primarily anti-chiropractic MDs) that such an event is impossible, because no spinal nerves supply the ear. Once, when I was testifying as an expert witness in a patientâs automobile accident case, the opposing attorney, his voice dripping with sarcasm, attacked me with this very story.
It is important to refute the charge specifically. The underlying physiological mechanism is called the somato-autonomic reflex, fully recognized in all modern medical and chiropractic textbooks. Its name describes the interaction between the muscular and skeletal system (soma, or body), and the autonomic (involuntary) portion of the nervous system. Signals initiated by spinal manipulation are transmitted via autonomic pathways to internal organs.

In the case of Palmerâs first adjustment, the relevant nerve pathway starts in the upper back, coursing up the neck and into the skull along the sympathetic nerves which eventually lead to the blood vessels in the ear. Proper functioning of the hearing apparatus depends on a normal blood supply, which in turn depends on an adequate nerve supply.

While it is true that there are no spinal nerves as such directly supplying the ear, it is absolutely untrue that no nerve pathway links the two areas. The pathway exists, and any claims to the contrary betray ignorance of fully accepted modern physiology research.

Further Examples of Manipulationâs Effects on Internal Organs

Just as there are autonomic pathways supplying the ear, similar pathways lead from the spine to all parts of the body. A broad array of research has verified that these pathways exist, and that in some instances spinal manipulation can positively affect problems caused by them. The work of Czech neurologist Karel Lewit, M.D., American orthopedic surgeon John McMillan Mennell, M.D., and others has been particularly helpful in spreading these concepts beyond the chiropractic community. Dr. Lewit has for many years successfully used spinal manipulation to treat tonsillitis, breathing problems, migraine, vertigo, and much more.[3]

An example of a potential future direction for joint medical-chiropractic research is found in the book Chiropractic: Interprofessional Research, a summary of research presented at the World Chiropractic Conference, held in Venice, Italy in 1982. A series of studies by chiropractors, working in concert with Italian medical doctors, demonstrated promising effects of chiropractic treatment in cases of vertigo, tinnitus (ringing of the ears), headaches, and visual disorders.[4]
There is far less research available concerning chiropracticâs effects on visceral (internal organ) disorders than exists in relation to lower back pain and other musculoskeletal problems. This is because the chiropractic profession has had to prioritize the research it could afford to pursue in the absence of significant government funding. Proving the validity of chiropractic manipulation for those conditions most commonly treated by chiropractors (low back pain, neck pain, and headaches) has been the highest priority.

There is, nevertheless, a growing body of literature, some of it published in peer-reviewed scientific journals, on the effects of manipulation for problems related to internal organ dysfunction. Some of these are controlled clinical trials, while others are thought-provoking case studies which point to the need for more extensive future research:

A randomized, controlled clinical study demonstrated that diastolic and systolic blood pressure decreased significantly in response to chiropractic adjustments of the thoracic spine (T1-T5), while placebo and control groups showed no such change. This study demonstrated short-term effects of manipulation on blood pressure, and indicates a need for studies on long-term effects.[5]

As noted earlier in this book, there have been two controlled clinical trials which studied the effects of spinal manipulation on dysmenorrhea. The results were quite promising, and further research is in progress.[6,7]

A study at the National College of Chiropractic showed a marked increase in the activity levels of certain immune-system cells (PMNs and monocytes) after thoracic spine manipulation. These increases were significantly higher than in control groups, who were given either sham manipulation or soft-tissue manipulation.[8]

A study involving 73 Danish chiropractors in 50 clinics showed satisfactory results in 94 percent of cases of chiropractic research:infant colicinfant colic. The results occurred within two weeks, and involved an average of three treatments.[9]

Several case studies have indicated that bladder dysfunction can be responsive to lower back manipulation.[10,11]

Lung volume and forced vital capacity (a measure of lung strength), were shown in a series of cases to increase after chiropractic adjustments.[12,13]

A 7-month-old infant suffering from chronic constipation since birth (with a history of hard, pellet-like stools following hours of painful straining) was restored to normal bowel function by full-spine and cranial adjustments.[14]

A two-year-old child medically diagnosed with asthma and enuresis (bedwetting) improved dramatically as a result of spinal adjustments, after medication had proved inadequate.[15]

Pelvic pain and pelvic organ dysfunction, in which there was no accompanying lower back pain, was shown in a case study to resolve fully with chiropractic manipulation of the lumbar spine, after numerous failed attempts at treating the symptoms medically.[16]

A 5-year-old girl, who was experiencing up to 70 seizures a day, was treated with upper neck adjustments and became virtually seizure-free.[17]

Further exploration of chiropracticâs effects on internal organ problems holds great promise. Studies are underway as this book goes to press, and many more are expected. This may turn out to be the most fertile area for chiropractic research in the Twenty-First Century.

The Chiropractic Perspective

Looking back over the material weâve covered, how would we best summarize the differences between the chiropractic approach and the standard medical model?

First and foremost, the chiropractic model views symptoms in a broad context of health and body balance, not as isolated aberrations to be suppressed and then forgotten. Chiropractors recognize the need for thorough evaluation of symptoms, but do not assume that the elimination of symptoms is the ultimate goal of treatment. Just as peace is not the absence of war, health is not the absence of disease symptoms. The true goal is sustainable balance. This is recognized by chiropractors and by holistic medical physicians as well.

While chiropractors are trained in state-of-the-art diagnostic techniques, and while chiropractic examination procedures overlap significantly with those used by conventional medical physicians, chiropractors evaluate the information gleaned from these methods from a perspective that recognizes the intricate structural and functional interplay between different parts of the body.
The contrasting medical and chiropractic diagnostic approaches to pain provide a case in point. In my experience, conventional medical physicians far more frequently than chiropractors make the assumption that the location of a pain is the location of its cause. Thus, knee pain is generally assumed to be a knee problem, shoulder pain is assumed to be a shoulder problem, etc. This pain-centered diagnostic logic frequently leads to increasingly sophisticated and invasive diagnostic and therapeutic procedures. (If physical examination of the knee fails to clearly define the problem, then the knee is x-rayed. If the x-ray fails to offer adequate clarification, then an MRI of the knee is performed, etc.)

Chiropractors also utilize these diagnostic tools. I refer some patients for x-rays and MRI studies. My point is not to criticize these machines, but to present an alternative diagnostic model. I have seen more than a few cases of knee trouble where this entire high-tech diagnostic scenario was played out, and the cause of the problem turned out to be in the lower back.

If the lower back is mechanically dysfunctional, and in need of spinal manipulation, this can often place unusual stress on the knees. In cases of this sort, one can spend months or years medicating the knee symptoms with painkiller pills and/or steroid injections, or performing knee surgery, without ever addressing the real problem. This is not an isolated hypothetical instance. It happens far too often.

Whole-Body Context

The chiropractic approach to musculoskeletal pain involves evaluating the site of pain in a whole-body context. Shoulder, elbow and wrist problems can of course be caused by problems in the shoulder, elbow and wrist but pain in all of these joints frequently has its source in the neck. Similarly, pain in the hip, knee, and ankle can also have its source at the site of the pain but in many cases the source lies in the lower back. The need to consider this chain of causation is built into the core of chiropractic training.

Chiropractors from D.D. Palmer onward have purposely refrained from assuming that the site of a symptom is the site of its cause. They have assumed instead that the source of the pain should be sought somewhere along the path of the nerves leading to and from the site of the symptoms.
Thus, a pain in the knee might come from the knee itself, but if we trace the nerve pathways between the knee and the spine, we find along the way possible areas of causation in or around the hip, in the deep muscles of the buttocks or pelvis, in the sacroiliac joints, or in the lower spine.

Furthermore, if an imbalance does exist in the lower spine (at the fourth lumbar level, for example), it might have its source right there at L4, or might in turn be a compensation for another joint dysfunction elsewhere in the spine, perhaps in the middle or upper back. Thus, an integrated, whole-body approach to structure and function is of great value.

For a patient with an internal organ problem, chiropractic diagnostic logic would include evaluation of those spinal levels which are the source of the nerve supply to the involved area, as well as consideration of possible nutritional, environmental and psychological causes. Chiropractic practice standards also mandate timely referral to a medical physician for diagnosis and/or treatment, for any condition that is acute and dangerous, or when a reasonable trial of chiropractic treatment (current standards in most cases limit this to about one month) fails to bring satisfactory results.

Wellness and the Chiropractic Model

The chiropractic model pays heed to patientsâ nutritional needs, exercise habits, work conditions, and psychological health. In many cases, particularly with regard to nutrition and exercise, the chiropractor will act as a teacher, directly counseling patients on proper diet or exercise methods. In other instances, chiropractors will make referrals to other health practitioners, or to appropriate classes in the community.

The traditional chiropractic philosophy I learned during my training anticipated in many respects the concepts that comprise the modern wellness paradigm. Aside from being taught the importance of good diet, exercise, and emotional health, we also learned that it is far better to practice prevention than to engage in crisis-care, and that health is far more than the absence of symptoms. These ideas together form a respectable foundation for a profession that seeks to practice holism.


1. Copland-Griffiths, Dynamic Chiropractic Today, p. 159

2. Bourdillion, J.F. Spinal Manipulation. pp. 205-206

3. Copland-Griffiths, op. cit. p. 162

4. Mazzarelli, Joseph, D.C. (editor). Chiropractic: Interprofessional Research. pp. 69-76.

5. Yates RG, Lamping DL, Abram NL, Wright C. “Effects of Chiropractic Treatment on Blood Pressure and Anxiety: A Randomized, Controlled Trial.” Journal of Manipulative and Physiological Therapeutics, 1988; 11: 484-488.

6. Kokjohn K, Schmid DM, Triano JJ, Brennan PC. “The Effect of Spinal Manpulation on Pain and Prostaglandin Levels in Women with Primary Dysmenorrhea.” Journal of Manipulative and Physiological Therapeutics, 1992; 15: 279-285.

7. Thomason, PR, Fisher BL, Carpenter PA, Fike GL. “Effectiveness of Spinal Manipulative Therapy in Treatment of Primary Dysmenorrhea: A Pilot Study.” Journal of Manipulative and Physiological Therapeutics. 1979; 2: 140-145.

8. Brennan PC, Kokjohn K, Katlinger CJ, Lohr GE, Glendening C, Hondras MA, McGregor M, Triano JJ. “Enhanced Phagocytic Cell Respiratory Burst Induced by Spinal Manipulation: Potential Role of Substance P.” Journal of Manipulative and Physiological Therapeutics, 1991; 14: 399-408.

9. Klougart N, Nillson N, Jacobsen J. “Infantile Colic Treated by Chiropractors: A Prospective Study of 316 Cases.” Journal of Manipulative and Physiological Therapeutics, 1989; 12: 281-288.

10. Falk, JW. “Bowel and Bladder Dysfunction Secondary to Lumbar Dysfunctional Syndrome.” Chiropractic Technique, 1990; 2: 45-48.

11. Borregard, PE. “Neurogenic Bladder and Spina Bifida Occulta: A Case Report.” Journal of Manipulative and Physiological Therapeutics, 1987; 10: 122-123.

12. Masarsky, CS and Weber M. “Screening Spirometry in the Chiropractic Examination.” ACA Journal of Chiropractic, February 1989; 23: 67-68.

13. Masarsky, CS and Weber M. Chiropractic and Lung Volumes A Retrospective Study. ACA Journal of Chiropractic, September 1986; 20: 65-68.

14. Hewitt, EG. “Chiropractic Treatment of a 7-Month-Old With Chronic Constipation: A Case Report. Proceedings of the National Conference on Chiropractic and Pediatrics (International Chiropractors Association), 1992; 16-23.

15. Bachman TR, Lantz, CA. “Management of Pediatric Asthma and Enuresis With Probable Traumatic Etiology.” Proceedings of the National Conference on Chiropractic and Pediatrics (International Chiropractors Association), 1991: 14-22.

16. Browning, JE. ” Mechanically Induced Pelvic Pain and Organic Dysfunction in a Patient Without Low Back Pain.” Journal of Manipulative and Physiological Therapeutics, 1990; 13: 406-411.

17. Goodman R. “Cessation of Seizure Disorder: Correction of the Atlas Subluxation Complex.” Proceedings of the National Conference on Chiropractic and Pediatrics (International Chiropractors Association), 1991: 46-56.©1993, Daniel Redwood, D.C.

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Written by Daniel Redwood DC

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