Chiropractic spinal adjustments and manual therapy primarily affect the spinal discs and facet (zygapophysial) joints. The studies below indicate that it is these joints that are responsible for chronic spinal pain.

The first study was Dr. Vert Mooney’s Presidential Address of the International Society for the Study of the Lumbar Spine. It was delivered at the 13th Annual Meeting of the International Society for the Study of the Lumbar Spine, May 29-June 2, 1986, Dallas, Texas. It was published in the August, 1987 issue of the journal spine, and titled:

Where Is the Pain Coming From?

Key Points from this article include:

1) “In the United States in the decade from 1971 to 1981, the numbers of those individuals disabled from low-back pain grew at a rate 14 times that of the population growth. This is a greater growth of medical disability than any other. Yet this growth occurred in the very decade when there was an explosion of ergonomic knowledge, labor-saving mechanical assistance devices, and improved diagnostic equipment. We apparently could not find the source of pain.”

2) Degenerative spine disease, like grey hair and wrinkled skin, has an onward march of pathologic changes. The incidence of back pain peaks in the middle years and diminishes in the aged. Consequently, degenerative arthritis of the spine cannot be defined as the major cause of chronic back pain.

3) “Six weeks to 2 months is usually enough to heal any stretched ligament, muscle tendon, or joint capsule. Yet we know that 10% of back ‘injuries’ do not resolve in 2 months and that they do become chronic.”

4) “Mechanical events can be translated into chemical events related to pain.”

5) “Mechanical activity has a great deal to do with the exchange of water and oxygen concentration” in the disc.

6) An important aspect of disc nutrition and health is the mechanical aspects of the disc related to the fluid mechanics.

7) The pumping action maintains the nutrition and biomechanical function of the intervertebral disc. Thus, “research substantiates the view that unchanging posture, as a result of constant pressure such as standing, sitting or lying, leads to an interruption of pressure-dependent transfer of liquid. Actually the human intervertebral disc lives because of movement.”

8) “In summary, what is the answer to the question of where is the pain coming from in the chronic low-back pain patient? I believe its source, ultimately, is in the disc. Basic studies and clinical experience suggest that mechanical therapy is the most rational approach to relief of this painful condition.”

9) “Prolonged rest and passive physical therapy modalities no longer have a place in the treatment of the chronic problem.”

The second article was published in the August 1993 issue of the journal Pain, and titled:

On the nature of neck pain, discography and cervical zygapophysial joint blocks

Key points from this article include:

1) To determine the prevalence of disc pain and zygapophysial joint pain occurring simultaneously in the same segment of the neck, 56 patients with post-traumatic neck pain underwent both provocation discography and cervical zygapophysial joint blocks.

2) Both a symptomatic disc and a symptomatic zygapophysial joint were identified in the same segment in 41% of the patients.

3) Discs alone were symptomatic in only 20% of the sample.

4) Zygapophysial joints were symptomatic but discs were asymptomatic in 23%.

5) Only 17% of the patients had neither a symptomatic disc nor a symptomatic zygapophysial joint at the segments studied.

6) Neck muscle injury “does not provide a satisfying model for persistent or chronic neck pain” because extremity muscle injuries heal rapidly, “in a matter of days or weeks.”

7) Persistent neck pain suggests injury to tissues that heal poorly or slowly, such as the intervertebral disc and the facet joints. “However, painful disorders of these structures are not demonstrable by plain radiography, computed tomography or magnetic resonance images.” [Key Point]

8) No findings on plain radiography, computed tomography or magnetic resonance images are correlated with pain. [Important]

9) Discography will stress a painful disc and reproduce a patient’s pain.

10) Anesthetizing a painful facet joint or the medial branch of the posterior primary rami that innervates a painful facet joint will completely eliminate its pain.

11) The most frequent finding was “both a symptomatic disc and a symptomatic zygapophysial joint at the same segment,” seen in 41%. [Note the most common finding was a segmental lesion, important for chiropractors.]

12) The second most frequent finding was a symptomatic zygapophysial joint, alone, with no disc involvement, found in 23%.

13) “This indicated that 64% of the sample had a symptomatic zygapophysial joint.” [41% + 23% = 64%]

14) The third most frequent finding was a symptomatic disc alone, with no zygapophysial joint involvement, at 20%.

15) This indicated that 61% of the sample had a symptomatic disc.

[41% + 20% = 61%]

16) [Consequently, the zygapophysial joint was more often involved in the patient’s pain than the disc, by 3%, 64% over 61%.]

17) “If cervical segments are fully investigated, it emerges that cervical discs are not the most common, primary source of neck pain.”

18) “A large proportion, if not the majority, of patients with post-traumatic neck pain have symptomatic zygapophysial joints.”

19) If the zygapophysial joint is the source of neck pain, and not the disc, major surgical intervention is not indicated.

The third included related study on the origins of spine pain was published in the April 1991 issue of the journal Orthopedic Clinics of North America, and titled:

The Tissue Origin of Low Back Pain and Sciatica:
A Report of Pain Response to Tissue Stimulation During Operations on the Lumbar Spine Using Local Anesthesia

Key points from this study include:

1) These authors performed 700 lumbar spine operations using only local anesthesia to determine the tissue origin of low back and leg pain.

2) “Sciatica could only be produced by stimulation of a swollen, stretched, or compressed nerve root.”

3) “Back pain could be produced by several lumbar tissues, but by far, the most common tissue or origin was the outer layer of the annulus fibrosis.”

4) These authors note that the opinion of British Neurologist Wyke (1980), “the disc is not an important source of low back pain because nerve endings are not present,” is mistaken, wrong.

5) These authors disagree that weak or strained muscles are a common source of low back pain because:

1. Many patients with back pain have strong muscles.
2. Back pain lasts much longer than pain caused by strained or overused muscles in other regions.

6) These authors reference six other studies that conclude that “the annulus fibrosus is the most common site of low back pain,” and that the compressed nerve root alone causes sciatica, and that normal nerve roots cause no pain at all.

7) In this study, these authors consecutively anesthetized successive tissues of the low back. Prior to anesthesia, each tissue was mechanically stimulated with mechanical force from blunt surgical instruments or by an electrical current.

8) “The patients were fully awake or only lightly sedated. During the course of the operation we stimulated each tissue and asked the patient to report any painful sensation.”

9) The lumbar fascia could be “touched or even cut without anesthesia.”

10) “The normal, uncompressed, or unstretched nerve root was completely insensitive to pain.”

11) “In spite or all that has been written about muscles, fascia, and bone as a source of pain, these tissues are really quite insensitive.” [Important]

12) The outer annulus is “the site” of a patient’s back pain.

13) Back muscles themselves are not a source of back pain. [This does not mean that muscle problems are unrelated to back pain because they can create altered biomechanical function that put inappropriate stresses on the pain sensitive annulus.]

14) The muscles, fascia, and bone are really quite pain insensitive. [Important]

The fourth included related study on the origins of spine pain was published in the August 1996 issue of the journal Spine, and titled:

Chronic Cervical Zygapophysial Joint Pain After Whiplash
A Placebo-Controlled Prevalence Study

Key points from this article include:

1) The authors developed a diagnostic double-blindfolded study using placebo-controlled local anesthetic blocks, to determine the prevalence of cervical zygapophysial joint pain among 68 patients with chronic neck pain after whiplash injury.

2) The prevalence of cervical zygapophysial joint pain (C2-C3 or below) was 60%.

3) “In a study in which single diagnostic blocks were administered to a large sample of patients with posttraumatic neck pain, the authors found the prevalence of cervical zygapophysial joint pain to be between 25% and 65%, depending on whether worst-case or best-case analysis was undertaken.”

4) “The prevalence was studied in a sample of patients with chronic neck pain after whiplash injury. This condition was selected because it is the most controversial, costly, and perhaps, common form of neck pain.”

5) “Anatomic studies have shown that the cervical zygapophysial joints are the only structures innervated by the medial branches of the cervical dorsal rami that might be considered a source of chronic pain.”

6) “The significant feature of the current study is that cervical zygapophysial joint pain emerged as very common.”

This article generated an invited published Point of View, which made several key points, including:

1) “There are thousands of patients with chronic pain after sustaining an acceleration-deceleration injury, who we physicians, in our great wisdom, have diagnosed as strain, muscle dysfunction, and pain behavior, when according to this study between 46% and 73% of these patients have pain localized to the cervical zygapophysial joint or its supporting ligaments.”

2) “This study reveals a single symptomatic segment in 26 of 31 patients completing the study in which the C2-C3 joint is the most common cause of upper cervical pain referral and headache and the C5-C6 joint is the most common source of lower cervical axial pain and referred arm pain.”

3) “Although muscle pain and tissue hyperalgesia may be an integral part of chronic cervical pain after whiplash injuries, such pain may be better explained as a secondary reflex reaction to injury of segmental supporting structures.”

The fifth included related study on the origins of spine pain was published in the May 28, 2004 issue of the journal BioMedical Central Musculoskeletal Disorders, and titled:

Prevalence of facet joint pain in chronic spinal pain of cervical, thoracic, and lumbar regions

Key points from this article include:

1) The facet joints of 500 consecutive patients with chronic, non-specific spine pain were evaluated.

2) “This prospective study of patients with chronic non-specific spinal pain involving the cervical, thoracic and lumbar regions, alone or in combination, demonstrated by spinal region that the prevalence of cervical facet (zygapophysial) joint pain in patients with neck pain was 55%, thoracic facet joint pain in patients with mid back or upper back pain was 42% and lumbar facet joint pain in patients with low back pain was 31%.”

3) Painful cervical facets were identified in 55% of patients with neck pain.

4) Painful thoracic facets were identified in 42% of patients with thoracic pain.

5) Painful lumbar facets were identified in 31% of patients with low back pain.

The sixth included related study on the origins of spine pain was published in the April 2006 issue of the Journal of Bone and Joint Surgery (Am), and titled:

Pain Generation in Lumbar and Cervical Facet Joints

Key points from this article include:

1) Facet joints are implicated as a major source of neck and low-back pain.

2) Paradoxically, studies have shown that degenerative lumbar facet joints can be asymptomatic while normal-appearing joints can be painful.

3) The lumbar facet joints are wholly responsible for about 15% of low back pain and partially responsible for about 50% of low back pain.

4) Extension strains injure the facet-joint capsule and cause pain.

5) 6% to 33% of whiplash-injured victims develop chronic pain.

6) The incidence of cervical facet pain is greater than that of lumbar facet pain.

7) The prevalence of cervical facets causing chronic neck pain is about 55%.

8) Many patients with facet pain “have no obvious radiographic abnormalities,” suggesting the pain is of capsular origin.