Chiropractic Models Through History

Chiropractic began in a single room in Davenport, Iowa, in 1895, and within a few decades it had grown into the largest drug free, hands on profession in the United States. Its history is a story of bold ideas, courtroom battles, family conflict, internal schisms and, more recently, a long effort to test its founding claims with modern research. Knowing that history helps you understand why chiropractors today describe their work in such different ways, and why the word "subluxation" still sparks debate.

Section 1The founding of chiropractic and D.D. Palmer

A restless self taught healer

Daniel David Palmer (1845 to 1913), usually called D.D., was born near Port Perry in what is now Ontario, Canada. He had little formal schooling, and when his family moved to the American Midwest he worked a string of jobs: schoolteacher, beekeeper, raspberry grower and grocer. He was a voracious reader with a deep interest in physiology, anatomy, spiritualism and the many unconventional healing systems of his day. Like many of his contemporaries, he distrusted the harsh drugs of regular physicians.

In the mid 1880s Palmer opened an office in Davenport, Iowa, as a magnetic healer. Magnetic healing descended from the work of Franz Anton Mesmer, an eighteenth century physician who taught that an invisible fluid, "animal magnetism," flowed through living things and that illness resulted from its obstruction. Practitioners passed their hands over the patient, or touched and stroked the body, to restore the flow. Palmer built a busy practice, and the idea that disease reflects an obstruction of some vital flow, and that the healer's hands can remove the obstruction, carried straight into his later thinking.

September 1895: Harvey Lillard

The founding story of chiropractic centers on Harvey Lillard, an African American janitor who worked in Palmer's office building. According to Palmer's account, Lillard had been nearly deaf for about seventeen years. He said that while exerting himself in a cramped, stooped position he had felt something give way in his upper back, and his hearing had failed soon after. Palmer examined him, found what he described as a vertebra "racked from its normal position," and, with Lillard face down, delivered a quick thrust using the spinous process as a lever. Palmer reported that Lillard's hearing improved afterward. Palmer reasoned that the displaced vertebra had pressed on a nerve and that restoring its position had restored the nerve's function.

Historians treat the details cautiously. The only firsthand accounts come from Palmer and from people close to him, and later family statements described the episode differently, including one version in which the trouble began when Lillard was startled by Palmer. Modern anatomy also offers a puzzle: the cochlear nerve is a cranial nerve that runs from the inner ear straight to the brainstem and does not pass through the thoracic spine, so a thoracic displacement could not compress the nerve of hearing. Whatever happened that day, the event served as the profession's founding moment, and Palmer quickly generalized from it. A few months later he reported relieving a patient's heart trouble with a similar adjustment, and he concluded that he had discovered a principle that applied to most disease.

Naming the new practice

Palmer asked a patient and friend, the Reverend Samuel Weed, to help name the method. They combined the Greek words cheir (hand) and praxis (practice or action) to form chiropractic, "done by hand." The name was meant to separate the new method from magnetic healing, from medicine with its drugs and surgery, and from osteopathy, which had appeared in Missouri about twenty years earlier. In 1897 Palmer began teaching the method in a school in Davenport, and his early classes were very small. One of his first graduates was his son, Bartlett Joshua, known as B.J.

Whether Palmer borrowed from osteopathy has been argued for more than a century. Andrew Taylor Still, a frontier physician, had announced osteopathy in 1874 and opened its first school in 1892, and Palmer is known to have discussed osteopathic ideas. The two systems shared the belief that structural problems in the spine cause disease, but they differed in mechanism. Still emphasized the free flow of blood ("the rule of the artery is supreme"), while Palmer emphasized the nervous system. Many historians conclude that both men drew from a shared pool of nineteenth century bonesetting, vitalism and drugless healing, and that each added his own synthesis.

Tone, Innate Intelligence and the displaced vertebra

Palmer's theory matured over the next fifteen years and is laid out in his 1910 book The Chiropractor's Adjuster. Three linked ideas sit at its center.

• Tone. Palmer taught that health depends on the normal degree of tension, firmness and activity in nerves and tissues. "Life is the expression of tone," he wrote. Too much tension produced overactivity, inflammation and heat; too little produced sluggishness and weakness. Disease was, at bottom, an abnormal tone.
• Innate Intelligence. Palmer described an inborn intelligence that runs the body, maintains tone and heals it, and he saw it as an individualized portion of a larger Universal Intelligence. The nervous system was the channel through which Innate expressed itself. This vitalist idea had religious overtones; late in life Palmer described chiropractic as having a moral and religious dimension.
• The displaced vertebra. Bones "out of place," especially vertebrae, could press on or stretch nerves, altering their tone and therefore the function of the tissues they supplied. Palmer claimed that about 95 percent of diseases were caused by displaced vertebrae and the rest by displacements of other joints. The adjustment, a specific thrust delivered by hand, was meant to correct the displacement and free the nerve.

Palmer's model mixed a testable claim (that spinal displacements compress nerves and cause organ disease) with a philosophical one (that an innate intelligence governs the body). The testable claim has not held up, as Section 4 explains; the philosophical claim cannot be tested by experiment at all. Read Palmer in the context of his era: in 1895 germ theory was young, many physicians still used mercury and bloodletting, and gentle drugless systems attracted millions of patients.

Prosecution, quarrels and death

Chiropractors who treated disease without a medical license risked prosecution. In 1906 D.D. Palmer was convicted in Iowa and chose to serve a short jail sentence rather than pay the fine. The same period brought a lasting break with his son. Financial pressures and personal conflict led D.D. to leave the Davenport school, and B.J. took control of it. D.D. spent his last years teaching and writing in Oklahoma, Oregon and California and sharply criticizing his son in print. He died in Los Angeles in 1913. A famous story holds that B.J.'s car struck his father during a homecoming parade in Davenport shortly before his death; the story was widely repeated and even litigated, but the death record lists typhoid fever, and historians still debate what role, if any, the parade incident played.

Section 2B.J. Palmer and the growth of the profession

The "Developer"

Bartlett Joshua Palmer (1882 to 1961), known as B.J., ran the Davenport school from about 1906 until his death more than half a century later. If D.D. was the discoverer, B.J. styled himself the Developer, and in many ways he built the profession that exists today. He was a gifted promoter, a showman and a tireless writer who produced dozens of volumes on chiropractic philosophy and practice (the "Green Books"). He was also autocratic, and several of his decisions split the profession he was building. His wife, Mabel Heath Palmer, taught anatomy at the school for decades, wrote an anatomy text for chiropractic students and was honored by students as the "First Lady of Chiropractic."

Under B.J. the school grew from a handful of students to an institution with more than a thousand students by the early 1920s. Its course, typically eighteen months to two years, was short by modern standards but not unusual for the time. B.J. preached an uncompromising version of his father's ideas: the subluxation interferes with the expression of Innate Intelligence through the nervous system, and the chiropractor's only job is to locate, analyze and correct it.

Spinography: x-ray comes to chiropractic

X-rays were discovered by Wilhelm Roentgen in 1895, the same year as the Lillard adjustment. In 1910 B.J. brought radiography into the chiropractic curriculum and called it spinography. He argued that films could show the misaligned vertebrae that chiropractors felt by hand, giving the subluxation an objective image. Spinography became a defining feature of chiropractic practice and led to analysis systems that measure the position of vertebrae on film, a tradition still visible in some upper cervical and structural techniques. It also brought later criticism, because full spine radiographs deliver radiation and modern guidelines advise imaging only when the history and examination suggest it will change management (see Chapter 7 on red flags and imaging).

The legal fight and the Morikubo case

In the early twentieth century every state had a medical practice act, and anyone who diagnosed or treated disease without a medical license risked arrest. Chiropractors were prosecuted by the thousands across the first decades of the century. In 1906 B.J. and colleagues founded the Universal Chiropractors' Association (UCA), which functioned as a kind of legal defense fund: members paid dues, and when one was arrested the association supplied lawyers.

The decisive early case came in 1907 in La Crosse, Wisconsin. Shegetaro Morikubo, a Japanese immigrant and recent graduate, was charged with practicing osteopathy without a license. His lawyer, Tom Morris, argued that chiropractic was a separate science with its own philosophy: osteopathy held that disease came from obstructed blood flow, while chiropractic held that it came from interference with nerve function through subluxations governed by Innate Intelligence. The jury acquitted. The Morikubo case had two lasting effects. It established a legal argument that chiropractic was distinct from both medicine and osteopathy, and it gave the profession a strong practical reason to emphasize its unique philosophy, because that philosophy was literally what kept chiropractors out of jail. Some historians argue that this legal history helps explain why the philosophical language of Innate and subluxation became so deeply rooted.

The long-term answer was a separate license. Kansas passed the first chiropractic licensing law in 1913. Other states followed one by one; in California, after hundreds of chiropractors were jailed in the early 1920s (many choosing jail over fines as a form of protest), voters approved a 1922 ballot initiative that created a chiropractic licensing board. Louisiana, in 1974, was the last state to license chiropractors. Chapter 10 places this fight in the larger story of American medical licensure.

Radio, showmanship and the neurocalometer

B.J. understood mass media early. In 1922 he launched one of the first commercial radio stations in the Midwest from the Davenport campus, with call letters said to stand for "Wonders of Chiropractic." Its mix of music, news and chiropractic messages (a young Ronald Reagan announced sports there in the early 1930s) made chiropractic a household word in the rural Midwest.

In 1924 B.J. introduced the neurocalometer (NCM), a handheld instrument with two temperature probes that a chiropractor glided along both sides of the spine. B.J. claimed that a difference in skin temperature between the two sides marked a nerve under pressure from a subluxation, and he declared the device essential to proper practice. It was leased rather than sold, at a price that was very high for the time, and the leases were tied to B.J.'s organization. Many chiropractors saw this as a commercial scheme and a betrayal of the hand based art. Faculty members resigned, enrollment at the Davenport school fell sharply, and B.J. lost control of the UCA. Paraspinal temperature measurement survived in later instruments, but research has not shown that side to side skin temperature differences reliably identify a subluxation or predict response to care.

Hole in One and the B.J. Palmer Research Clinic

Around 1930 B.J. concluded that the most important subluxations were not scattered along the spine but concentrated at the top, at the atlas (C1) and axis (C2). He reasoned that the upper cervical region surrounds the brainstem and upper spinal cord, where all nerve traffic between brain and body passes, so a subluxation there would interfere with the whole body. His Hole in One (HIO) technique analyzed the upper cervical spine on radiographs and corrected it with a precise, light, very fast "toggle recoil" thrust delivered with the patient lying on the side. Several modern upper cervical techniques trace their ancestry to HIO, each with its own radiographic analysis and adjusting method.

In 1935 B.J. opened a research clinic in Davenport that admitted seriously ill patients, documented them with radiographs, skin temperature readings and electrocardiography, and treated them with upper cervical adjustments. Its detailed case records had no control groups, so they cannot tell us whether patients improved because of the adjustments, because of rest and nursing care, or by chance. That gap between careful observation and controlled testing is a theme that runs through the whole history of manual therapies.

Section 3Straight, mixer and reform movements

An argument as old as the profession

Almost as soon as chiropractic existed, its practitioners disagreed about its boundaries. Two questions drove the disagreement. First, should a chiropractor do anything besides adjust the spine by hand? Second, does a chiropractor diagnose and treat disease, or only find and correct subluxations? The answers produced two broad camps, and their names stuck.

• Straights held that chiropractic is the location, analysis and correction of vertebral subluxations by hand, and nothing else. Adding other therapies, they argued, diluted chiropractic and turned it into a weaker copy of medicine. B.J. Palmer was the leading straight.
• Mixers "mixed" the adjustment with other natural therapies of the day: physiotherapy modalities such as heat, cold, electrical stimulation and traction; nutrition and diet; exercise; and hydrotherapy. B.J. used the word as an insult, but mixers came to wear it comfortably. They generally accepted that chiropractors should diagnose patients and broadened training in the medical sciences.

Mixer schools appeared within the first decade. One of D.D. Palmer's early students, John Howard, opened a school in Chicago in 1906 that became the center of the mixer tradition, with longer courses, laboratory sciences and dissection. Willard Carver, a lawyer who had defended D.D. Palmer and later became a chiropractor, opened schools in Oklahoma and elsewhere that taught a structural approach and the use of adjunctive therapies. These schools tended to welcome higher entry requirements and accreditation earlier, while straight schools often resisted rules they saw as written in the image of medicine.

Organizations follow the split

Professional associations formed around each camp. After B.J. lost control of the UCA in the neurocalometer controversy, he founded the International Chiropractors Association (ICA) in 1926 as the voice of straight chiropractic. In 1930 the UCA merged with another group to form the National Chiropractic Association (NCA), which leaned toward the mixer side. In 1963 the NCA reorganized as the American Chiropractic Association (ACA), now the largest chiropractic association in the United States. Attempts to merge the two national bodies failed repeatedly, and both still exist.

The mixer side also drove educational reform. Beginning in the 1930s and 1940s, NCA leaders, especially John Nugent, pressed schools to lengthen programs, require prior college study, become nonprofit and meet published standards. That work produced the Council on Chiropractic Education (CCE), which in 1974 was recognized by the federal government as the accrediting agency for chiropractic programs. Straight schools at first objected, and for a time a separate straight accrediting agency held federal recognition, but today all U.S. programs that lead to the Doctor of Chiropractic degree are accredited by the CCE.

The objective straight position

In the 1970s a group of chiropractors pushed the straight position in a new direction. Rather than claiming to treat disease, they explicitly removed disease from chiropractic's job description. In this objective straight view, the chiropractor's sole objective is to locate, analyze and facilitate the correction of vertebral subluxations so that the body's innate capacity can express itself fully; the chiropractor does not diagnose or treat any condition, and patients with health problems are referred to the appropriate provider. The position has a legal and ethical logic: it avoids claiming effects on disease that cannot be supported, and it frames care as a wellness service. Critics respond that offering ongoing care to people with no symptoms, for a lesion whose existence and health effects have not been demonstrated, still makes an implicit health claim.

The reform movement

At the other end, some chiropractors concluded that the profession's founding theory was wrong and that its future lay in being specialists in neuromusculoskeletal care. In 1984 a group formed a reform association whose members publicly rejected the idea that subluxations cause organic disease, limited their scope to conditions such as back pain, neck pain and headache, and sought close cooperation with medicine. The group was small and was criticized by other chiropractors, but its arguments anticipated a much broader trend.

From the 1990s onward, a growing number of chiropractic researchers and educators adopted the language of evidence based practice, defined as the integration of the best available research evidence with clinical expertise and patient values. Papers in the profession's own journals called for retiring the subluxation as a clinical theory, while others defended it as a legitimate subject for research. International identity work led by the profession's world federation in the early 2000s described chiropractors as "the spinal health care experts in the health care system," and later proposals cast chiropractors as primary spine care providers who triage and manage spinal complaints in collaboration with medical clinicians.

Techniques across the spectrum

Chiropractors use more than a hundred named techniques, and technique choice partly tracks philosophy. The most widely used is diversified technique, a family of high velocity, low amplitude (HVLA) thrusts applied anywhere in the spine and extremities. Others include drop table, flexion distraction, instrument assisted and low force methods, and the upper cervical techniques descended from B.J.'s HIO work, which remain most common in straight practice. Chapter 4 covers the mechanics of the thrust.

Section 4Subluxation models over time

One word, two meanings

The word subluxation means different things in medicine and in chiropractic, and confusing the two causes endless misunderstanding. In medicine, a subluxation is a partial dislocation: the joint surfaces have shifted so that they are only partly in contact, and the displacement is usually visible on imaging. Examples include atlantoaxial subluxation in rheumatoid arthritis, shoulder subluxation after a stroke weakens the rotator cuff and deltoid, and the radial head subluxation of "nursemaid's elbow" in toddlers. A medical subluxation is a structural injury that can threaten nerves or the spinal cord, and it is often a reason not to manipulate.

The chiropractic subluxation is a different idea: a functional or minor positional disturbance of a spinal segment, with joint surfaces fully in contact, that is said to affect nerve function and health. Its definition has changed several times over 130 years, and following those changes is the best way to understand both its appeal and the scientific criticism it has drawn.

Model 1: the bone out of place

D.D. Palmer and early B.J. Palmer described a static misalignment: a vertebra displaced from its normal position, pressing on a spinal nerve where it exits through the intervertebral foramen (IVF). The popular image was a "foot on a garden hose," cutting off the flow of nerve impulses to the organs. Early chiropractors also used charts linking each vertebral level to particular organs, called the meric system, so that, for example, a subluxation found in the midthoracic spine was linked to stomach trouble.

Anatomy and experiment did not support it as a general mechanism. In normal spines the nerve root occupies only part of the foramen, roughly a third to a half of its cross sectional area, with the rest filled by fat, vessels and connective tissue. A 1973 cadaver study by an anatomist found that the foramina could not be narrowed enough to touch the nerve roots without forces that would fracture or dislocate the spine, far beyond anything a minor misalignment could produce. Nerve roots can be compressed in the foramen, but by disc herniation, osteophytes, facet hypertrophy or loss of disc height (foraminal stenosis), conditions that cause radicular pain and neurologic signs (Chapter 5) rather than silent disease of internal organs. Also, many organs receive autonomic innervation from several segments and from the vagus nerve, which does not pass through the vertebral foramina at all.

Model 2: fixation and motion

Beginning in the 1930s, the Belgian chiropractor Henri Gillet and colleagues shifted attention from position to motion. Gillet developed motion palpation, in which the examiner feels each segment move as the patient bends and rotates, and proposed that the real problem was a fixation, a segment that had lost its normal mobility. In the 1970s Leonard Faye popularized motion palpation in North America. This model fit naturally with the joint play and end feel concepts covered in Chapter 3, and it aligned chiropractic with the manual medicine and physical therapy traditions, which also treat hypomobile segments with mobilization and manipulation. Osteopathic medicine developed a parallel concept, somatic dysfunction.

Model 3: the vertebral subluxation complex

In the 1970s and 1980s Faye and others expanded the idea into the vertebral subluxation complex (VSC), which described the subluxation as a set of interacting changes rather than a single displaced bone. The classic version had five components, and later authors added more, such as vascular and connective tissue components.

Model 4: consensus and neurophysiology

In the 1990s the association representing chiropractic schools in North America adopted a consensus definition that described the subluxation as a complex of functional, structural or pathological joint changes that compromise neural integrity and may influence organ function and general health. A 2005 international guideline on chiropractic training issued under a global health agency defined it more narrowly as a lesion or dysfunction of a joint or motion segment in which alignment, movement integrity or physiological function is altered while contact between joint surfaces remains intact. Notice the trend: from a displaced bone, to lost motion, to a broad functional disturbance described in cautious language ("may influence").

Current research on how spinal manipulation works seldom uses the word subluxation at all. Instead, it studies measurable effects of the thrust. Leading models propose that the mechanical input of manipulation triggers a cascade of neurophysiological responses: changes in peripheral mechanoreceptor and nociceptor input, spinal reflexes and motor neuron excitability, and supraspinal pain modulation, including reduced temporal summation of pain. Other researchers propose that segmental dysfunction alters sensorimotor integration, the way the brain processes sensory input from the spine and plans movement, and that manipulation can normalize it. These hypotheses are testable and are being tested, but they explain short-term changes in pain and motor control, not the cure of internal disease.

What the evidence shows

Researchers have examined the subluxation concept from several angles.

• Reliability of detection. For a lesion to be studied, examiners must agree on where it is. Studies of static palpation, motion palpation and leg length checks generally find poor to fair agreement between examiners (kappa values often below 0.4), while palpation for tenderness and pain provocation tends to be more reliable. Radiographic marking of vertebral position is more reliable, but small positional differences are common in people without symptoms.
• Causation. A widely cited 2009 review applied the Bradford Hill criteria for causation (strength, consistency, temporality, dose response, biological plausibility and others) to the chiropractic subluxation and found no supportive evidence that it causes disease.
• Visceral conditions. Randomized trials that compared real manipulation with a convincing sham for conditions such as childhood asthma, hypertension and painful menstruation have generally found that both groups improve similarly, which points to nonspecific effects such as attention, expectation and natural history. Systematic reviews conclude that there is no reliable evidence that manipulation treats organic disease.
• Musculoskeletal pain. By contrast, spinal manipulation has a modest, real evidence base for low back pain, neck pain and some headaches, discussed in Section 5 and Chapter 11. The benefit does not depend on accepting the traditional subluxation theory.

Subluxation in billing and records

The word survives in law and billing even where clinical thinking has moved on. When Medicare began covering chiropractic in 1972 (effective the following year), it limited coverage to manual manipulation of the spine to correct a subluxation. A chiropractor can document the subluxation with a radiograph or with physical examination findings summarized by the acronym PART. At least two of the four elements must be present, and one of them must be asymmetry or range of motion abnormality.

Diagnosis coding systems also include codes for segmental and somatic dysfunction and for vertebral subluxation complex. Because coverage rests on this terminology, even chiropractors who reject the traditional theory must document "subluxation" for Medicare patients: vocabulary is shaped by law and payment as well as by science.

Section 5Contemporary chiropractic identity and practice

The profession today

Chiropractic is now a licensed health profession in all fifty U.S. states, the District of Columbia and U.S. territories, and it is practiced in about ninety countries, with legal regulation in many of them. The United States has roughly 70,000 licensed chiropractors, more than any other country. Most work in private practice, alone or in small groups, but a growing number work in multidisciplinary clinics, hospitals, community health centers, sports organizations, the military health system and veterans' health care. The Department of Veterans Affairs began placing chiropractors in its medical centers in the early 2000s, and chiropractic is now part of many VA pain management teams.

Surveys suggest that about one in ten American adults sees a chiropractor in a given year. The overwhelming majority of visits are for musculoskeletal complaints: low back pain is the most common reason, followed by neck pain, headache and extremity joint problems. Patient satisfaction is consistently high.

Education, licensure and scope

To become a Doctor of Chiropractic (DC) in the United States, a student completes undergraduate prerequisites (the accreditation standard requires at least 90 semester hours, and many programs prefer or require a bachelor's degree) and then a doctoral program of about four academic years, usually around 4,200 instructional hours. Programs are accredited by the Council on Chiropractic Education. The curriculum is roughly divided among basic sciences (anatomy, physiology, biochemistry, pathology, microbiology), clinical sciences (physical, orthopedic and neurologic diagnosis, laboratory diagnosis, radiology), chiropractic technique and patient management, and a supervised clinical internship. Graduates take a series of national board examinations covering basic sciences, clinical sciences, clinical competency and practical skills, and then meet the licensing requirements of the state where they will practice, including continuing education to keep the license.

Scope of practice is set by each state and varies. Chiropractors in every state examine and diagnose patients, may order or take radiographs, and treat with manipulation and other manual methods. Many states also permit physiotherapy modalities, rehabilitative exercise, nutritional counseling and, in some states, ordering of laboratory tests or advanced imaging. Chiropractors generally do not prescribe drugs or perform surgery, and the question of limited prescribing remains contested within the profession, in part because a drugless identity has been central since D.D. Palmer.

Competing identities

Because of the history described in Sections 1 to 4, the profession still debates what chiropractic is. Several identity models coexist.

• Spinal health care experts and primary spine care. The profession's world federation adopted the identity "the spinal health care experts in the health care system" in the early 2000s. A related proposal casts the chiropractor as a primary spine care provider: the first contact clinician for most spinal pain, who screens for serious pathology, manages most cases conservatively and coordinates referral for the rest, much as a primary care physician does for general health.
• Neuromusculoskeletal specialist. Close to the reform tradition, this model sees chiropractors as experts in conservative care for muscles, joints and nerves throughout the body, working in teams with physicians, physical therapists and others.
• Wellness and vitalistic care. Close to the straight tradition, this model emphasizes the nervous system, the body's self healing capacity and regular care for people without symptoms. Its supporters see it as continuity with the profession's philosophy; critics point out the lack of evidence that regular adjustments improve health in people without symptoms.

Several frank internal debates follow from these identities. One concerns routine full spine radiographs, which guidelines advise against without clinical indications. Another concerns long prepaid care plans, which sit uneasily with evidence that most acute back pain improves within weeks. A third concerns vaccination. D.D. Palmer opposed vaccination, and some chiropractors still voice doubts, but vaccines are among the best supported interventions in public health, vaccine advice lies outside chiropractic training and scope, and responsible professional bodies emphasize that patients should get vaccine information from those qualified to give it.

A contemporary evidence informed visit

In an evidence informed practice, a new patient visit follows the same logic described in Chapter 7: a careful history, screening for red flags such as cancer, infection, fracture, cauda equina syndrome and vascular disease, a focused physical and neurologic examination, a working diagnosis, and a discussion of options, risks and expected benefit before consent. Treatment usually combines manipulation or mobilization with soft tissue work, exercise, education about pain (Chapter 6) and advice to stay active. Progress is measured with validated outcome tools and reassessed within a few weeks. Patients who do not improve, or who develop new signs, are referred or co-managed.

What the evidence supports

Chapter 11 explains how to read research, but a brief summary helps place chiropractic practice in context. For acute low back pain, a 2017 meta-analysis found that spinal manipulation produced modest improvements in pain (about one point on a ten point scale) and function, with only minor, transient adverse effects. For chronic low back pain, a large 2019 review found that manipulation works about as well as other recommended therapies such as exercise, with small effects. A major 2017 clinical guideline for internal medicine physicians listed spinal manipulation among the nondrug options for both acute and chronic low back pain and recommended nondrug options as first line care. For neck pain, manipulation and mobilization, especially combined with exercise, show short-term benefit. For cervicogenic headache there is some supportive evidence, while evidence for migraine and tension type headache is weaker and mixed. For nonmusculoskeletal conditions such as asthma, hypertension, infant colic and otitis media, controlled evidence does not show benefit.

Safety

Manipulation is generally safe in appropriately screened patients, but it is not risk free. Minor adverse events are common: roughly a third to a half of patients report local soreness, stiffness, headache or fatigue after a treatment, usually starting within a day and resolving within one to two days. Serious adverse events are rare. The most discussed is cervical artery dissection with stroke after neck manipulation. Population studies have found that people with this kind of stroke are more likely to have recently seen a chiropractor, but they are equally likely to have recently seen a primary care physician, which suggests that many patients already had a developing dissection whose early symptoms (neck pain and headache) led them to seek care. Whether manipulation can trigger or worsen a dissection in some cases remains debated, so careful screening and informed consent are standard. Other rare serious events include worsening of disc herniation with cauda equina syndrome, and fractures in patients with osteoporosis, cancer in bone or other conditions that weaken the spine (Chapter 4).

Words worth knowing