The Effects of Spinal Manipulation
on the Musculoskeletal System
Spinal manipulation is one of the most ancient forms of treatment for musculoskeletal complaints, primarily for back pain and neck pain.
In 1992, Robert Anderson, MD, PhD, DC, was the Director of Manual Medicine at the San Francisco Spine Institute, as well as Professor of Anthropology at Mills College in Oakland, California.
At that time (1992), Scott Haldeman, DC, PhD, MD, was Associate Clinical Professor of Neurology at the University of California, Irvine, California.
In 1992, the second edition of Dr. Haldeman’s book, Principles and Practice of Chiropractic, was published. Dr. Anderson wrote the first chapter of Dr. Haldeman’s book, titled (1):
“Spinal Manipulation Before Chiropractic”
Dr. Anderson notes that historically (for a least 2,500 years), spinal manipulation had been practiced in many parts of the world, primarily to treat musculoskeletal disorders. He presents the evidence of spinal manipulation being applied by a variety of providers in vast geographic regions, including: Bohemian (Czechoslovakia), China, Egypt, England, Finland, Greece, India, Japan, Latin America, Norway, Russia, and Wales.
In many ways, the history of joint manipulation parallels the history of civilization. Another important review of manipulation through the ages was published in The Journal of Manual & Manipulative Therapy in 2007 and titled (2):
A History of Manipulative Therapy
This review makes these comments:
“Manipulative therapy has known a parallel development throughout many parts of the world. The earliest historical reference to the practice of manipulative therapy in Europe dates back to 400 BCE.”
“Historically, manipulation can trace its origins from parallel developments in many parts of the world where it was used to treat a variety of musculoskeletal conditions, including spinal disorders.”
“It is acknowledged that spinal manipulation is and was widely practiced in many cultures and often in remote world communities such as by the Balinese of Indonesia, the Lomi-Lomi of Hawaii, in areas of Japan, China and India, by the shamans of Central Asia, by sabodors in Mexico, by bone setters of Nepal as well as by bone setters in Russia and Norway.”
“Historical reference to Greece provides the first direct evidence of the practice of spinal manipulation.”
“Hippocrates (460–385 BCE), who is often referred to as the father of medicine, was the first physician to describe spinal manipulative techniques.”
“Claudius Galen (131–202 CE), a noted Roman surgeon, provided evidence of manipulation including the acts of standing or walking on the dysfunctional spinal region.”
“Avicenna (also known as the doctor of doctors) from Baghdad (980–1037 CE) included descriptions of Hippocrates’ techniques in his medical text The Book of Healing.”
“Nobody questions these early origins of manipulative therapy.”
Prior to the modern era, for hundreds of years in developed and primitive societies throughout the world, practitioners of manipulation were known as bonesetters (2). All of this changed in 1874, and the global seat of change was in the United States of America.
Andrew Taylor Still was a second-generation physician who became disillusioned with medicine following the death (from disease) of three of his children. Dr. Still conceived a theory whereby health could only be maintained and, therefore, disease defeated, by maintaining normal function of the musculoskeletal system (2). In 1892, Still established the American Osteopathic College in Kirksville, Missouri. By the time of his death in 1917, 3,000 Doctors of Osteopathy had graduated from his school.
In 1895, “natural healer” Daniel David (DD) Palmer reasoned that when a vertebra was out of alignment, it caused pressure on nerves. In 1897, Palmer opened his first college, The Palmer College of Cure, now known as Palmer College of Chiropractic, Davenport, Iowa (2).
In 1910, Palmer’s son Bartlett Joshua (BJ) Palmer, introduced the use of X-rays into Chiropractic. History records (2):
“The G. I. Bill at the end of World War II enabled thousands of returning soldiers to bolster the ranks of the chiropractic profession.”
“This influx seemed to provide an impetus that would propel the chiropractic profession to today’s status where it boasts 35 schools and colleges worldwide and, in the Western world at least, it is second only to the medical profession as a primary care healthcare provider.”
How Does Spinal Manipulation Work?
Pain Theory Background
In 2017, a comprehensive and authoritative assessment of the chiropractic profession appeared in the orthopedic medical journal Spine, titled (3):
The Prevalence, Patterns, and Predictors of
Chiropractic Use Among US Adults:
Results From the 2012 National Health Interview Survey
The survey results indicated that 93% of patients go to chiropractors for the management of musculoskeletal pain syndromes. Specifically, 63% go to chiropractors for low back pain, and 30% for neck pain. Additionally, chiropractic spinal manipulation is very effective for the management of back and neck pain (3). The study showed:
- 65% of the patients reported that chiropractic care helped their condition “a great deal.”
- 26% of the patients reported that chiropractic care helped their condition “somewhat.”
- Only 3% reported that the chiropractic care they received did not help them.
In randomized clinical trials comparing chiropractic spinal manipulation to prescription pain medicines for chronic low back and neck pain, chiropractic manipulation was significantly more effective, registered no significant side effects, and displayed stable long-term clinical benefits (at the one year follow-up assessment) (4, 5).
How does chiropractic spinal manipulation
benefit people with spinal pain complaints?
The Concept of Proprioception
Proprioception is a sensory input from the peripheral musculoskeletal body (muscles, joints, tendons, ligaments, etc.) to the brain (central nervous system). Proprioceptive signals transmit mechanical information, especially mechanical factors such as position and movement. This concept is well-stated by attorney Chris Crowley and physician Henry Lodge, MD, in their book Younger Next Year, in a section they refer to as (6):
“The Balancing Act”
“Now it’s time to think about your brain and a concept called proprioception—the deceptively simple notion that you have to know where the different parts of your body are at all times.”
“Your body is aware of exactly where each limb is in space every second, because each muscle, tendon, ligament and joint sends thousands of nerve fibers back to the brain through the spinal cord. Those fibers signal every nuance gradation of contraction, strength, muscular tone, orientation, position and movement at every moment of the day.”
“Your brain keeps careful track of the location of every muscle and joint in you body every second, all day, every day, waiting for you to need the information.”
Proprioception is both conscious and subconscious. In 1965, researchers discovered an incredibly important function for proprioception: pain control.
In 1965, pain researchers became aware that the proprioceptive signals to the brain could block the pain signal to the brain. This concept was originally proposed by pain researchers Ronald Melzack and Patrick Wall (7). Their theory is known as the Gate Control Theory of Pain. Ronald Melzack, PhD, is a Canadian psychologist. Patrick Wall, MD (d. 2001), was a British neuroscientist and pain expert, as well as the first editor of the journal Pain.
In 2002, the British Journal of Anaesthesia published a study reaffirming the validity of the Gate Theory of Pain in an article titled (8):
Gate Control Theory of Pain Stands the Test of Time
An oversimplified explanation of their Gate Control Theory of Pain is that the pain electrical signal to the brain can be blocked by non-painful electrical signals arising from other sensory afferents, especially from joint proprioceptors. Practically, this would mean that prolonged or static positions would reduce proprioception, allowing the pain signal to more readily enter the brain for pain perception. Similarity, if a person’s joints lost or reduced their normal movement arc, there would be a proportionate reduction of the proprioceptive sensory input to the brain. This would allow pain signals to enter the brain because the pain gate would be open.
As noted above, chiropractic’s Daniel David Palmer believed that when a vertebra was out of alignment, it caused pressure on nerves (2). A specific directional manipulation (the chiropractic spinal adjustment) would improve alignment and reduce nerve pressure.
Palmer’s “nerve pressure” theory is probably correct in only a minority of chiropractic patients. It was officially challenged by a vocally pro-chiropractic orthopedic surgeon from Saskatchewan, CAN. Dr. William H. Kirkaldy-Willis published his theory as to how/why chiropractic spinal manipulation helped those suffering from back pain in the journal Canadian Family Physician in 1985 (35 years prior to this writing), titled (9):
Spinal Manipulation in the Treatment of Low Back Pain
Dr. Kirkaldy-Willis (d. 2006) was a Professor Emeritus of Orthopedics and director of the Low-Back Pain Clinic at the University Hospital, Saskatoon, Canada. The abstract from his article makes these comments:
“Spinal manipulation, one of the oldest forms of therapy for back pain, has mostly been practiced outside of the medical profession.”
“Over the past decade, there has been an escalation of clinical and basic science research on manipulative therapy, which has shown that there is a scientific basis for the treatment of back pain by manipulation.”
“Most family practitioners have neither the time nor inclination to master the art of manipulation and will wish to refer their patients to a skilled practitioner of this therapy.”
“The physician who makes use of this resource will provide relief for many patients.”
Dr. Kirkaldy-Willis notes that 80% of the population will experience low back pain sometime during their adult life. At any given time, 20-30% of the adult population is suffering from low back pain. Low back pain is the second most common cause of worker loss of productivity.
Yet, in disagreement with chiropractic’s Daniel David Palmer, Dr. Kirkaldy-Willis argues that less than 10% of low back pain is due to pressure or entrapment of spinal nerves. He notes that it is unlikely that spinal manipulation replaces a vertebra that is out of alignment.
In contrast, Dr. Kirkaldy-Willis applies Melzack and Wall’s Gate Theory of Pain to the chiropractic adjustment in his explanation as to how manipulation helps with pain.
Dr. Kirkaldy-Willis begins his explanation by noting that with positional (alignment) problems there is a shortening of periarticular connective tissues and intra-articular adhesions may form. This orthopedic principle is supported by many others (10, 11, 12, 13, 14, 15, 16, 17, 17). This intra-articular and periarticular fibrosis would reduce joint motion. He proposes that a specific line-of-drive manipulation (chiropractic spinal adjustment) could break these adhesions and/or remodel fibrosis, also supported by others (11, 12, 13, 15, 16, 17, 18). He cites support for these concepts, including:
- Following joint manipulation, there is consistently a measureable increase in the range of motion.
- As a rule, there is an initial increase in symptoms after the first few manipulations probably as a result of breaking adhesions and tissue fibrosis. He states:
“In almost all cases, however, this increase in pain is temporary and can be easily controlled by local application of ice.”
“Patients undergoing manipulative treatment must therefore be reassured that the initial discomfort is only temporary.”
“However, the gain in mobility must be maintained during this period to prevent further adhesion formation.”
Dr. Kirkaldy-Willis then applies the improved articular motion to Melzack and Wall’s Gate Theory of Pain. He notes that this theory has “withstood rigorous scientific scrutiny,” stating:
“The central transmission of pain can be blocked by increased proprioceptive input.”
Pain is facilitated by “lack of proprioceptive input.”
“Increased proprioceptive input in the form of spinal mobility tends to decrease the central transmission of pain from adjacent spinal structures by closing the gate. Any therapy which induces motion into articular structures will help inhibit pain transmission by this means.”
Dr. Kirkaldy-Willis notes that at the end of the manipulation range of motion, “the limit of anatomical integrity is encountered. Movement beyond this limit results in damage to the capsular ligaments.” Consequently, joint manipulation “requires precise positioning of the joint at the end of the passive range of motion and the proper degree of force to overcome joint coaptation” (to overcome the resistance of the joint surfaces in contact). He concludes:
“With experience, the manipulator can be very specific in selecting the spinal level to be manipulated.”
“The physician who makes use of this resource will provide relief for many back pain patients.”
Today (2020) this “Orthopedic Gate Theory” explanation for the mechanism of benefits from manipulation for pain control is widely popular. Yet, Dr. Kirkaldy-Willis also offers a concomitant reflex neurological model. He supports that during manipulation, the stretching of joint ligaments (capsules) will trigger a reflex that inhibits local musculature, also improving motion and closing the pain gate.
An update to the effects of spinal manipulation was published last year (2019) in the journal Spine, titled (19):
Neurophysiological Effects of High Velocity and Low Amplitude
Spinal Manipulation in Symptomatic and Asymptomatic Humans:
A Systematic Literature Review
The objective of this study was to summarize the evidence of the neurophysiological effects of spinal manipulative therapy (SMT) with high velocity low amplitude thrust (HVLA-SMT). The authors searched the literature until July 2018 and only used controlled studies of at least moderate quality. They found 18 studies that met their inclusion criteria that involved 932 participants. Most studies on spinal manipulation focus on pain mechanisms and pain control.
The authors note that spinal manipulative therapy with high-velocity low amplitude thrust (HVLA-SMT) is effective in reducing low back pain (LBP), and applies to both acute and chronic nonspecific LBP. They agree that spinal manipulation has both neurophysiological and biomechanical influences, and support that manipulation increases proprioception, stating:
“The mechanical force of spinal manipulation primarily affects afferent neurons in the paraspinal tissue and triggers neurophysiological responses in the peripheral and central nervous system, eventually leading to pain inhibition.”
The evidence presented in this study supports that spinal manipulation increases proprioception, which eventually leads to pain inhibition. This is consistent and supportive of Dr. Kirkaldy-Willis’s application of Melzack and Wall’s Gate Theory of Pain, above.
Also in 2019 (April), a study was published in the Journal of Pain titled (20):
Decreased Neurologic Pain Signature Activation Following
Thoracic Spine Manipulation in Healthy Volunteers
In this study, researchers from Stanford University employed functional magnetic resonance imaging (fMRI) on ten healthy volunteers to objectively measure pain intensity following spinal manipulation. This study was funded by the National Institute of Health, USA.
The authors note that: “Spinal manipulation is commonly used when managing patients with neck and back pain.” Although they support the rationale that spinal manipulation elicits a mechanical effect on the spine that leads to therapeutic mechanical changes within the spine, they wanted to explore if central (brain) mechanisms were also being activated. The results of this study showed that spinal manipulation activates brain regions associated with pain inhibition.
It has been observed for decades that spinal manipulation helps control pain. This study adds to the evidence, using the best available evidence (functional MRI), showing that spinal manipulation works in pain reduction, in part, by inhibiting pain-processing regions of the brain. Once again, the results of this study are consistent and supportive of Dr. Kirkaldy-Willis’s application of Melzack and Wall’s Gate Theory of Pain.
A few months later in 2019 (October), this same group published a follow-up study titled (21):
Evidence for Decreased Neurologic Pain Signature Activation
Following Thoracic Spinal Manipulation
in Healthy Volunteers and Participants with Neck Pain
Once again, these authors used functional magnetic resonance imaging (fMRI) to investigate the effect of thoracic spinal manipulation on pain-related brain activity. They assessed 16 subjects with acute/subacute neck pain and compared them to 10 healthy volunteers. The spinal manipulation was a high-velocity low-amplitude end-range force directed to the T4-T5 motion segment. The brain fMRI images were performed on a 3T magnetic resonance scanner.
The authors note that fMRIs can map pain processing in the central nervous system. They also note that the perception of pain is not encoded by a single brain area but distributed throughout the brain.
Spinal manipulation is a mechanical thrust to spinal joints slightly beyond their passive range of motion. It is a common treatment for neck and back pain, theorized to mechanically affect the spine leading to therapeutic mechanical changes. Yet, spinal manipulation’s therapeutic action may also be mediated by inhibiting the central nervous system.
This study confirmed that there is a centrally (brain) mediated therapeutic action of spinal manipulation for pain reduction. The authors note:
“The findings provide evidence that spinal manipulation may alter the processing of pain-related brain activity within specific pain-related brain regions.”
“A growing body of evidence is pointing towards neurophysiologic mechanisms of action underlying the pain modulating effects of spinal manipulation including both spinal and supraspinal mechanisms.”
Consistent with the other studies above, and in support of the proprioception closure of the pain gate, these authors note:
“Spinal manipulation is known to activate large diameter mechanoreceptors that in turn can inhibit the transmission of nociceptive signals at the spinal cord.”
Earlier this year (2020), another study on this topic was published in the journal Cureus titled (22):
The Effect of High Velocity Low Amplitude
Cervical Manipulations on the Musculoskeletal System:
As the title indicates, the objective of the study was to describe how cervical manipulation could impact musculoskeletal disorders. A systematic search of the literature was carried out using PubMed; inclusion criteria was randomized controlled trial manuscripts published in peer-reviewed journals with individuals of all ages from 2005 to 2020. Subjects with skeletal muscle or health problems were evaluated as to the effects of cervical manipulation, comparing them with control subjects receiving placebo or another type of treatment.
The authors note that the number of people suffering from skeletal muscle problems is constantly increasing. They attribute this to work activities that lead to prolonged wrong positions for a period of time.
Pertaining to spinal manipulation, the authors note:
“Spinal manipulation is a manual therapy technique used by chiropractors, osteopaths, physiotherapists and some doctors to treat skeletal muscle problems.”
“In manual therapy, high velocity low amplitude (HVLA) cervical manipulation techniques are frequently used.”
“The use of high velocity low amplitude (HVLA) techniques is growing as a therapeutic option.”
“Cervical manipulations are effective in management of cervicalgia, epicondylalgia, temporomandibular joint disorders, and shoulder pain.”
Both cervical manipulation and thoracic manipulation may lead to significant cervical pain improvement. The review of the literature presented indicates that spinal manipulation activates the supraspinal (brain and brainstem) neurological pain inhibitory control system. The authors note:
“Manipulation involves segmental activation of inhibitory pathways that may lead to changes in pressure pain thresholds even at a distance [away from] of the manipulated area.”
“HVLA techniques are able to produce more local hypoalgesia than other manual therapy techniques.”
“The results of the research show that HVLA techniques, on subjects with musculoskeletal disorders, are able to influence pain modulation, mobility, and strength both in the treated area and at a distance.”
For thousands of years and throughout the world there are observations that spinal manipulation helps people with musculoskeletal pain, especially spinal pain. For more than one hundred years, chiropractors, patients, governments, insurance companies, and scientists have realized that chiropractic spinal adjusting (specific manipulation) not only helps people with a variety of musculoskeletal pain syndromes, but that it probably works, at least in part, as a consequence of the activation of brain pain control circuitry.
When spinal joints have reduced movement, the pain gate at that level is open. Chiropractic adjusting (specific manipulation) increases the firing of the proprioceptors, creating a neurological sequence of events that closes the pain gate.
Proprioceptive integrity is a significant factor in the state of the pain gate. Improved proprioception closes the pain gate. Chiropractic adjusting improves proprioception.
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“Authored by Dan Murphy, D.C.. Published by ChiroTrust® – This publication is not meant to offer treatment advice or protocols. Cited material is not necessarily the opinion of the author or publisher.”