Subluxation Models, Basic Science Concepts and Applied Principles

The subluxation is the concept around which chiropractic was built, and it is also the concept most debated inside and outside the profession. The board expects you to define it precisely in each of its historical and current forms, to explain the neurological and biomechanical models proposed to account for it, and to know what adjustments and manipulation actually do to joints, nerves and muscles. Just as important, you must be able to tell a patient honestly which parts of the story are well established, which are plausible hypotheses, and which are unsupported.

Section 1Defining the subluxation

The medical meaning

In medicine and orthopedics, a subluxation is a partial or incomplete dislocation: the articular surfaces have lost their normal congruity but remain partly in contact. It is a structural diagnosis usually visible on imaging. Examples include atlantoaxial subluxation in rheumatoid arthritis (an atlantodental interval above 3 mm in an adult), acromioclavicular separation, and radial head subluxation in a young child ("nursemaid's elbow"). A luxation is a complete dislocation with no contact between joint surfaces. When a radiologist writes "subluxation," this is what is meant, and it may indicate instability rather than a lesion to adjust.

Historical chiropractic definitions

D.D. Palmer described a vertebra "displaced" or "racked" from its normal position, impinging on nerves and altering their tone. Stephenson's 1927 textbook defined a vertebral subluxation as a vertebra that has lost its proper juxtaposition with the vertebra above, below or both, to a degree less than a luxation, which impinges nerves and interferes with the transmission of mental impulses. That definition contains four elements often taught as a sequence: misalignment, occlusion of an opening (the intervertebral foramen), pressure on nerves and interference with transmission. This is the "bone out of place" model: a static positional fault that narrows the foramen and compresses a nerve.

Current consensus definitions

From the 1970s onward the profession shifted from a static positional lesion to a functional one centered on altered motion. The main current definitions are:

Medicare and the PART criteria

For US Medicare, chiropractic coverage is limited to manual manipulation of the spine to correct a subluxation. Since 2000, the subluxation may be demonstrated either by x-ray or by physical examination using the PART criteria. At least two of the four must be present, and one must be asymmetry or range of motion abnormality:

• Pain and tenderness (location, quality, intensity)
• Asymmetry or misalignment (static or sectional, segmental level)
• Range of motion abnormality (increase or decrease of sectional or segmental mobility)
• Tissue and tone changes (in skin, fascia, muscle, ligament)

Medicare covers active or corrective treatment that is expected to produce functional improvement (indicated with the AT modifier); maintenance care is not considered medically necessary under Medicare and requires advance notice to the patient if billed. Subluxation and segmental dysfunction also have diagnostic codes in the ICD system (subluxation complex, vertebral; and segmental and somatic dysfunction), each specified by spinal region.

Related terminology

The vertebral subluxation complex

The vertebral subluxation complex (VSC) model, developed by Leonard Faye and later expanded by Charles Lantz, describes subluxation as a cascade involving several tissues rather than a single displaced bone. Faye's five components are:

1. Kinesiopathology (spinal kinesiopathology): altered motion and position, including hypomobility, hypermobility, aberrant motion, altered instantaneous axis of rotation and misalignment. This is the starting point in most versions of the model.
2. Neuropathophysiology: irritation, compression or facilitation of neural tissue; altered afferent input; reflex effects on muscle, vessels and viscera.
3. Myopathology: hypertonicity, spasm, trigger points, guarding, then weakness, inhibition and atrophy (for example, deep multifidus).
4. Histopathology: inflammation, edema, fibrosis, adhesions and degenerative changes in capsule, ligament, disc and cartilage.
5. Biochemical abnormalities (pathophysiology): inflammatory mediators (prostaglandins, bradykinin, histamine, substance P), altered metabolism and stress hormones.

Lantz added separate components for connective tissue pathology, vascular abnormalities (vasomotor changes, venous congestion) and the inflammatory response. The components interact: restricted motion irritates nociceptors, which causes muscle guarding, which further restricts motion, and prolonged immobility leads to connective tissue changes and degeneration.

Subluxation, degeneration and the evidence

Kirkaldy Willis described a three phase degenerative cascade of the motion segment: dysfunction (painful, reversible facet and disc dysfunction), instability (capsular laxity, disc resorption, abnormal motion) and stabilization (osteophytes, facet hypertrophy and stiffening, sometimes with stenosis). Chiropractic authors connect the dysfunction phase with subluxation and argue that restoring motion may slow the cascade, a plausible but unproven claim.

Honest teaching must also note the limits. There is no validated reference standard for detecting a subluxation; the examination procedures used (motion and static palpation, leg checks, thermography, posture analysis) have low interexaminer reliability; and no high quality study has shown that subluxations cause visceral disease or that correcting them improves general health. Some authors propose retiring the term in favor of "segmental dysfunction"; others retain it as a historical, legal and clinical construct while acknowledging that its effects beyond pain and function are hypotheses.

Section 2Neurological models of subluxation

Each neurological model proposes a route by which a dysfunctional motion segment could affect the nervous system and, through it, other tissues. They range from well supported (altered afferent input and pain) to plausible but untested in humans (somatovisceral effects of minor joint dysfunction). The board expects you to know the mechanism, the key names, and the state of the evidence for each.

Joint receptors and afferent input

The facet joint capsules, ligaments, disc annulus and paraspinal muscles are richly innervated. Wyke classified articular receptors into four types:

Mechanoreceptor input (types I to III, carried by large A beta fibers, together with muscle spindle and Golgi tendon organ afferents) informs the central nervous system about position and movement and normally inhibits nociceptive transmission. Nociceptive input (type IV, carried by small A delta and C fibers) drives pain, muscle guarding and autonomic responses. The gate control theory (Melzack and Wall, 1965) proposed that large fiber input closes a "gate" in the dorsal horn (substantia gelatinosa) through inhibitory interneurons, while small fiber input opens it. Gate control is one explanation for why movement and manipulation reduce pain.

Facilitation

The osteopathic physiologist Irvin Korr described the facilitated segment in the 1940s: sustained afferent bombardment from a lesioned area holds the spinal cord neurons of that segment in a state of partial depolarization, so they fire in response to stimuli that would not affect neighboring segments. Korr called the segment a "neurological lens" that focuses and amplifies input. Facilitated segments showed lowered thresholds for reflex muscle contraction, increased sympathetic activity (skin conductance, vasomotor changes) and tenderness. Facilitation is the forerunner of the modern concept of central sensitization, a well documented amplification of neural signaling in the dorsal horn and brain that underlies many chronic pain states.

Dysafferentation and somatosomatic reflexes

Dysafferentation, a term popularized by Seaman and Winterstein in the late 1990s, describes an imbalance in afferent input from a dysfunctional segment: decreased mechanoreception (because the segment moves less) and increased nociception (because inflamed or stressed tissues fire). The result is altered central processing that may cause pain, altered motor control, and autonomic changes. The model is consistent with well established research showing that people with spinal pain have impaired proprioception (larger joint position errors in neck pain), altered muscle recruitment and changes in sensorimotor cortical maps.

Somatosomatic reflexes link somatic input to somatic output. Nociceptive input from a facet joint or disc produces reflex muscle spasm and guarding, which can perpetuate pain and restriction (the pain, spasm, pain cycle). Joint injury and effusion also produce arthrogenic muscle inhibition: after a first episode of low back pain the deep multifidus on the painful side shows segmental atrophy and delayed activation that may persist after pain resolves, which supports specific stabilization exercise. The somatosomatic model is the best supported of the neurological models.

Nerve compression and traction

The intervertebral foramen (IVF) is bounded superiorly and inferiorly by the pedicles, anteriorly by the vertebral bodies and disc (and in the cervical spine the uncovertebral joint), and posteriorly by the facet joint and ligamentum flavum. It contains the spinal nerve roots and dorsal root ganglion, the recurrent meningeal (sinuvertebral) nerve, segmental arteries, veins and fat. In the lumbar spine the nerve root occupies roughly one third to one half of the foraminal area.

• Sharpless (1975) showed that a pressure of only about 10 mm Hg on a dorsal root could reduce conduction by up to about half within 15 to 30 minutes, whereas peripheral nerve needed far higher pressure. Nerve roots lack a full perineurium and are more vulnerable than peripheral nerves.
• Compression of a normal nerve root produces only a brief discharge; compression of the dorsal root ganglion or of a chronically inflamed root produces sustained ectopic firing. Inflammation (for example, from nucleus pulposus contact) is therefore as important as pressure in radicular pain.
• Low pressures (around 5 to 10 mm Hg) impair venous return and intraneural nutrition, causing edema and ischemia before conduction is lost.
• Crelin (1973) found in cadaver spines that the foramina could not be narrowed enough to touch the nerve by displacing vertebrae within normal limits. Critics note that cadavers lack muscle tone, inflammation and swelling, but the study shows that a minor positional fault alone is unlikely to compress a healthy root.

Nerve compression is clearly real when caused by pathology (disc herniation, osteophytes, facet hypertrophy, stenosis), and these produce radiculopathy that you will examine with dermatomes, myotomes and reflexes. Whether minor subluxation compresses roots is unproven. A related traction model holds that abnormal spinal mechanics can tension the dura, cord and roots (the neuraxis lengthens several centimeters from full extension to full flexion), producing neural mechanosensitivity detectable with neural tension tests such as the straight leg raise and upper limb tension tests.

Somatovisceral and viscerosomatic reflexes

Somatovisceral reflexes are changes in visceral function evoked by somatic stimulation. The Japanese physiologist Akio Sato and colleagues showed in anesthetized animals that noxious or innocuous stimulation of skin, muscle or joints alters heart rate, blood pressure, gastric motility, bladder contraction and adrenal secretion. Reflexes from a segmental area acted mainly through the segmental sympathetic outflow (for example, pinching the abdominal skin inhibited gastric motility), whereas stimulation of distant areas such as a paw evoked supraspinal reflexes (pinching a hindpaw increased gastric motility through the vagus). These experiments prove that somatovisceral reflexes exist. They do not show that a spinal subluxation produces clinically meaningful organ dysfunction in humans, or that adjusting it improves organ disease; clinical trials have not supported that claim.

Viscerosomatic reflexes run the other way: visceral afferents enter the cord with sympathetic nerves and converge on the same dorsal horn neurons as somatic afferents, so the brain misattributes visceral pain to the somatic area (referred pain, by convergence projection), and segmental reflexes produce paraspinal muscle guarding, skin hyperesthesia and tissue texture change. This direction is well established and clinically vital: visceral disease can look exactly like a mechanical spinal problem.

Axoplasmic aberration and trophic effects

Neurons transport proteins, organelles and neurotrophic factors along their axons by axoplasmic transport: fast anterograde transport (about 200 to 400 mm per day, kinesin on microtubules), slow transport (about 0.2 to 5 mm per day, cytoskeleton and soluble enzymes) and retrograde transport (dynein, returning trophic signals such as nerve growth factor to the cell body). Korr proposed that nerves have a trophic function independent of impulses, maintaining the health of target tissues (muscle fiber type, for example, depends on its motor neuron). The axoplasmic aberration model holds that mechanical deformation of nerves at a subluxated segment could slow transport and deprive target tissues of trophic support. Experimental compression in animals does impair axoplasmic flow, and "double crush" phenomena in peripheral nerves are consistent with it, but no study shows that minor joint dysfunction impairs axoplasmic transport in humans.

Neuroimmunomodulation

The nervous and immune systems communicate in both directions. Sympathetic fibers innervate the thymus, spleen, lymph nodes and bone marrow, and immune cells carry adrenergic receptors; the hypothalamic pituitary adrenal axis releases cortisol, which suppresses inflammation; sensory neuropeptides (substance P, CGRP) promote neurogenic inflammation; and cytokines signal back to the brain to produce sickness behavior. The neurodystrophic hypothesis proposes that neural dysfunction at a subluxation alters this communication and lowers tissue resistance. Small studies have found transient changes after a single manipulation (priming of neutrophil respiratory burst, reduced production of inflammatory cytokines such as TNF alpha and IL 1 beta by stimulated blood cells). These effects are small, short lived and of unknown clinical significance, and there is no evidence that chiropractic care improves resistance to infection or outcomes of immune disease.

Vascular insufficiency

Vascular models propose that subluxation alters blood flow by: segmental sympathetic vasoconstriction causing local ischemia; venous congestion in the IVF and epidural venous plexus causing edema around the root; or mechanical effects on the vertebral artery, which runs through the transverse foramina of C6 to C1 and turns sharply over the atlas, so that upper cervical dysfunction might reduce vertebrobasilar flow. Venous congestion is supported as a mechanism of root ischemia in stenosis; the other proposals remain largely theoretical. The vertebral artery's course is also why cervical manipulation carries a rare risk discussed in Section 4.

Section 3Biomechanical models and basic science concepts

The motion segment

The motion segment (functional spinal unit) is the smallest unit that shows the mechanical behavior of the spine: two adjacent vertebrae with the intervening disc, facet (zygapophyseal) joints, ligaments and muscles. The disc and the two facets form a three joint complex: a change in one (disc narrowing, for example) changes loading in the others. Each segment has six degrees of freedom, three rotations and three translations about three axes. In the standard right handed coordinate system, the x axis runs side to side (flexion and extension are rotations about it), the y axis runs vertically (axial rotation), and the z axis runs front to back (lateral bending). Translations along these axes are lateral shear, axial compression or distraction, and anterior or posterior shear.

The neutral zone is the initial part of the range near neutral where the segment moves with little resistance; the elastic zone follows, where motion meets increasing resistance from passive tissues. Panjabi's stabilizing system has three subsystems: passive (vertebrae, discs, ligaments), active (muscles) and neural control. Injury or degeneration enlarges the neutral zone, and the active and neural subsystems must compensate; clinical instability occurs when they cannot.

Facet orientation and regional motion

The thoracolumbar junction changes abruptly from rotation permitting thoracic facets to rotation resisting lumbar facets, usually at T11 to T12 or T12 to L1. Stress concentrates there, which is why compression and burst fractures cluster at this level.

Coupled motion

Coupled motion is the consistent association of motion about one axis with motion about another. The classic patterns:

• Lower cervical (C2 to C7) and upper thoracic: lateral bending is coupled with axial rotation to the same side. In right lateral bending the vertebral bodies rotate right (toward the concavity) and the spinous processes swing left (toward the convexity), a consequence of the inclined facet planes.
• Lumbar: in neutral, lateral bending is classically coupled with rotation of the bodies to the opposite side (toward the convexity), with spinous processes toward the concavity. Measured lumbar coupling varies between individuals and with posture, so the rule is a tendency, not a law.
• Upper cervical: C1 to C2 rotation is coupled with slight vertical translation because of the biconvex articular surfaces.

The osteopathic Fryette laws state the same principles: in neutral, side bending and rotation occur to opposite sides (type I, group curves such as scoliosis); in flexion or extension, they occur to the same side (type II, single segment dysfunction); and motion introduced in one plane reduces motion available in the others (law III). In structural scoliosis the vertebral bodies rotate toward the convexity, so the rib hump appears on the convex side.

The instantaneous axis of rotation

When a rigid body moves in a plane, at any instant there is a line about which it is rotating: the instantaneous axis of rotation (IAR). For sagittal motion of a healthy lumbar segment, the IAR lies near the posterior part of the disc or the upper endplate of the lower vertebra; for lower cervical flexion it lies in the body of the vertebra below. The path traced by successive IARs is the centrode. In degenerated or injured segments the IARs are scattered and displaced, which increases shear and abnormal facet loading. In three dimensions the equivalent is the helical axis of motion, which combines rotation about and translation along a single axis. Biomechanical models of subluxation describe it as a segment with altered range, altered quality of motion and a displaced IAR, and propose that adjusting restores a more normal axis.

Disc and facet biomechanics

The intervertebral disc has three parts. The nucleus pulposus is a hydrated gel of proteoglycans (mainly aggrecan) and type II collagen whose water content falls with age. The annulus fibrosus consists of concentric lamellae of type I (outer) and type II (inner) collagen, with fibers in alternate layers running about 30 degrees from horizontal in opposite directions, so half the fibers resist rotation in each direction. The cartilaginous endplates anchor the disc and allow diffusion of nutrients, because the adult disc is largely avascular. Only the outer third of the annulus is innervated, by the sinuvertebral nerve posteriorly and branches of the gray rami laterally.

Under compression the nucleus is pressurized and pushes outward, tensing the annular fibers (hoop stress) and bulging the endplates. In neutral standing, the disc carries roughly 80 percent or more of the compressive load and the facets the rest; the facet share rises in extension and as the disc narrows. The facets mainly resist anterior shear and axial rotation in the lumbar spine. Classic intradiscal pressure measurements at L3, expressed relative to standing (100 percent), are about 25 percent supine, 75 percent side lying, 140 percent sitting upright, 150 percent standing flexed and 185 percent sitting flexed, with higher values when lifting with a flexed spine. Later in vivo studies found relaxed sitting closer to standing, but the board still teaches the classic order. Flexion combined with rotation and repeated loading produce posterolateral annular fissures and herniation. Discs imbibe fluid overnight and lose height during the day, so the spine is stiffer and more vulnerable to flexion loading in the first hour after rising.

Spinal tissues are viscoelastic: they show creep (continued deformation under a constant load), stress relaxation (falling load at constant deformation), hysteresis (energy lost on loading and unloading) and stiffness that increases with loading rate. A ligament's load deformation curve has a toe region (crimped collagen straightens), a linear (elastic) region, a plastic region with microfailure, and failure. Sustained flexion postures creep ligaments and reduce reflex protection from paraspinal muscles for some time afterward, a mechanism for injury after prolonged stooping.

Joint play and the paraphysiological space

Joint play (Mennell) is the small amount of accessory movement (glide, distraction, rotation) a joint allows that cannot be produced by voluntary muscle action but is necessary for normal pain free motion. End play is the springy give felt at the end of passive range. Sandoz described the zones of joint motion used to explain manipulation: the active range, which the patient produces; the passive range, which the examiner can add and which ends at the elastic barrier of resistance; the paraphysiological space, a small extra range beyond the elastic barrier entered by a high velocity, low amplitude thrust and usually accompanied by cavitation; and the limit of anatomical integrity, beyond which ligaments and capsule are damaged (sprain, subluxation in the medical sense, dislocation).

Mobilization techniques are graded (Maitland grades I to IV, small or large amplitude within the available range; grade V is manipulation). End feel describes the quality of resistance at the end of passive range: normal end feels are bony (hard), capsular (firm) and soft tissue approximation; abnormal end feels include muscle spasm, springy block (loose body or meniscus), empty (pain stops motion before resistance, suggesting serious pathology) and a hard end feel in a joint that normally ends softly.

Tissue response to injury and immobilization

Immobilization harms every tissue in the motion segment. In ligament and capsule, water and glycosaminoglycans are lost, collagen fibers lie closer together and form abnormal cross links, and newly formed collagen is laid down randomly, producing contracture and adhesions; ligament strength and stiffness fall, and the bone ligament junction weakens through subperiosteal resorption. Articular cartilage, which is nourished by diffusion driven by loading and motion, loses proteoglycans, softens and thins. Muscle atrophies within days, especially slow oxidative fibers in antigravity muscles, and muscles immobilized in a shortened position lose sarcomeres. Bone loses mineral (Wolff's law in reverse). Recovery after remobilization takes much longer than the period of immobilization, months for ligament insertions. In animal studies, experimentally fixed lumbar segments developed facet joint adhesions and degenerative changes that increased with the duration of fixation and were only partly reversed when motion was restored. These findings form the basic science rationale for early, controlled motion and for the proposal that persistent segmental hypomobility contributes to degeneration.

Section 4Etiology of subluxation and the effects of adjustment and manipulation

Proposed causes: physical, chemical and emotional stressors

Following D.D. Palmer's traumas, toxins and autosuggestion, chiropractic texts group the causes of subluxation (or of segmental dysfunction) into three classes of stressor, mirroring the triad of health:

These categories are consistent with the biopsychosocial model, and the physical and psychosocial risk factors for spinal pain are well studied. What is not established is a causal chain from these stressors through a specific subluxation to disease elsewhere in the body.

What happens during a thrust

A high velocity, low amplitude (HVLA) thrust has three phases. The doctor takes up slack to the elastic barrier with a preload (roughly 20 to 150 newtons depending on region), delivers a brief thrust to a peak force, then resolves. Thrust duration is typically about 100 to 200 milliseconds. Peak forces are commonly reported around 400 to 550 newtons for prone thoracic and sacroiliac thrusts and around 100 to 150 newtons for cervical thrusts. Force, velocity and duration vary between practitioners, and the velocity and duration appear to determine much of the afferent response.

Cavitation

The audible "pop" of manipulation is cavitation. When a synovial joint is gapped quickly, pressure in the synovial fluid falls, dissolved gases (largely carbon dioxide) come out of solution and a gas cavity forms. Early studies of the metacarpophalangeal joint attributed the sound to bubble collapse; real time imaging later showed that the sound coincides with cavity formation (tribonucleation, the sudden separation of joint surfaces). After cavitation the joint space is wider on imaging and there is a refractory period of about 20 minutes before the joint can cavitate again, as the gas slowly redissolves. In the spine, cavitations are often multiple and frequently occur at segments other than the one targeted. Importantly, clinical outcomes in trials do not depend on whether a cavitation was heard, so the sound is not a reliable sign that an adjustment was "successful."

Mechanical effects

• Gapping of the facet joints, greater with side posture manipulation than with positioning alone, which may release entrapped synovial folds (meniscoids) and stretch contracted capsule.
• Possible disruption of periarticular adhesions formed during hypomobility (supported indirectly by animal data).
• Immediate changes in segmental stiffness, which in some studies decrease in patients who improve.
• Small, transient intersegmental motion. There is no evidence that manipulation produces a lasting change in vertebral position visible on imaging, so "putting a bone back in place" is not an accurate description.

Neurophysiological effects

• Afferent discharge. The thrust strongly stimulates muscle spindles (group Ia and II), Golgi tendon organs (Ib) and joint mechanoreceptors in paraspinal tissues; their response is sensitive to thrust velocity and duration.
• Reflex muscle responses. A brief reflex EMG burst occurs in paraspinal muscles within milliseconds, often followed by reduced resting muscle activity. The H reflex (a measure of motor neuron excitability) is transiently depressed after lumbar manipulation.
• Hypoalgesia. Pressure pain thresholds rise both locally and at remote sites, and temporal summation of pain (a marker of dorsal horn sensitization) decreases, suggesting spinal and supraspinal pain modulation, including descending inhibition.
• Autonomic responses. Cervical mobilization and manipulation can produce short lived sympathoexcitation (increased skin conductance, changes in skin temperature, heart rate and blood pressure), which accompanies the hypoalgesic effect.
• Central effects. Studies report changes in sensorimotor integration and cortical processing after manipulation; their clinical meaning is still uncertain.
• Contextual effects. Expectation, the therapeutic relationship and the ritual of care contribute substantially. Contemporary models describe a mechanical force that sets off a cascade of peripheral, spinal and supraspinal responses, shaped by these nonspecific factors.

Clinically, as Chapter 9 explained, these effects translate into modest short term reductions in pain and disability for low back pain, neck pain and cervicogenic headache, comparable to other recommended conservative treatments.

Adverse events and their rates

Population based case crossover studies found that people under 45 with vertebrobasilar stroke were more likely than controls to have seen a chiropractor in the preceding week, but they were equally likely to have seen a primary care physician. The most plausible explanation is that a dissection already in progress causes neck pain and headache, which lead patients to seek care. A national stroke scientific statement concluded that a causal association has not been established but that patients should be informed of the association before cervical manipulation. For perspective, the risks of common alternatives are not zero: long term NSAID use causes serious gastrointestinal complications in roughly 1 to 2 percent of users per year.

Section 5Applied principles and wellness

Phases of care

Evidence for maintenance care

The best evidence comes from a Nordic pragmatic trial of patients with recurrent or persistent low back pain who had responded well to an initial course of chiropractic care. Those randomized to individually scheduled maintenance visits had about 13 fewer days with bothersome pain over a year, at the cost of about two additional visits. A secondary analysis found the benefit concentrated in patients with a psychologically "dysfunctional" profile (high pain impact and distress). Smaller trials suggest that ongoing manipulation can sustain gains in chronic low back pain. There is no trial evidence that routine adjustments in asymptomatic people prevent spinal disorders or other disease. Maintenance care is therefore reasonable for selected patients with recurrent problems who responded well, with the plan individualized, explained honestly and reviewed against outcomes.

Prevention and health promotion

As portal of entry providers who see patients frequently, chiropractors are well placed to deliver evidence based prevention within their scope:

Useful benchmarks: adults should accumulate 150 to 300 minutes of moderate (or 75 to 150 minutes of vigorous) aerobic activity each week, with muscle strengthening on at least two days, and older adults should add balance training. Brief tobacco counseling follows the 5 As: ask, advise, assess readiness, assist and arrange follow up. Patients should be directed to appropriate providers for recommended screening and immunizations, consistent with public health guidance.

Helping patients change behavior

The transtheoretical model (stages of change) describes readiness for change: precontemplation (not considering change), contemplation (thinking about it), preparation (planning soon), action (recently changed, under six months) and maintenance (sustained over six months), with relapse common and expected. Advice should match the stage: information and empathy in precontemplation, a concrete plan in preparation, problem solving and support in action. Motivational interviewing uses the OARS skills (open questions, affirmations, reflective listening and summaries) to draw out the patient's own reasons for change, and self efficacy (confidence in one's ability) is one of the strongest predictors of success.

Communicating principles to patients honestly

• Use accurate, reassuring language. Phrases such as "your spine is out," "your disc has slipped" or "your neck is degenerating" create fear and can worsen outcomes (a nocebo effect). Explain instead that the joint is stiff and sensitive, that spines are strong, that degenerative findings are common in people without pain, and that movement helps.
• Describe what an adjustment does in terms the evidence supports: it improves movement and reduces pain for many people in the short term, mainly through effects on the nervous system. Avoid claiming that it puts bones back in place, cures disease or boosts immunity.
• Obtain informed consent as a conversation, often summarized as PARQ: procedures, alternatives, risks (including common benign reactions and rare serious ones) and questions.
• Set goals and measure outcomes with validated tools (numeric pain rating, Oswestry, Neck Disability Index, patient specific functional scale) and re-examine at regular intervals; discharge, change course or refer when progress stalls.
• Recommend care in proportion to need. Prepaid long term plans sold on the basis of imaging findings or fear are ethically problematic; plans should follow the patient's response and goals.
• Present philosophy as philosophy. It is appropriate to share the profession's respect for the body's self healing capacity, provided the patient understands which claims are supported by evidence and which are beliefs.

Words worth knowing