How does Chiropractic work?

Chiropractic was evolved as an empirical trade by DD Palmer in the late 1800s.  He was a teacher and grocer, who later became a “magnetic healer”.  Nine years later he conceived the idea of chiropractic.  His technique was based on the “adjustment” of bones. Palmer claimed that “a subluxed vertebra… is the cause of 95% of all diseases… the other 5% is caused by displaced joints other than those of the vertebral column“.

After a court case which ruled that chiropractic was a legitimate form of therapy it was marketed as a science and DD Palmer later claimed to be a philosopher.

DD Palmer started a school of chiropractic, perhaps not surprising with his teaching background, which allowed chiropractic to proliferate.  He repeatedly contended that he was not practicing medicine and had been imprisoned for practicing medicine without a licence.  His son took over the school of chiropractic and considered declaring chiropractic a religion (perhaps for the tax benefits available in the USA at that date).

The object of this post is not to give a critical overview of chiropractic.  Instead Paul Ingraham’s excellent commentary at is recommended.

What is unlikely to be disputed is that chiropractic is a large industry, and clearly there must be client satisfaction for it to survive commercially.

Where patient benefit results a “scientific” explanation might be of secondary importance. However an importance exists in that by an understanding the degree or frequency of benefit might be improved, or extrapolated to other illnesses.

Unfortunately chiropractors have proffered many explanations of their treatment which have little rational support. Often the “explanations” are no more than hollow jargonizing. It seems that a (perhaps the main) reason is to enhance their prestige and credibility as “science based” practitioners. Some claims (such as “correcting leg length inequality”) are fraudulent. Ironically it is this attempt at establishing “credibility” which does most to discredit chiropractic. The chiropractor could be well advised not to explain the reasons why their treatment is beneficial, and simply offer the service, letting it speak by results.

The foundation of chiropractic has been the management of vertebral pain by manipulative treatment, particularly rotary and hyperextension manipulation.  A “successful” manipulation, usually associated with satisfying clicks from the vertebral column, often dramatically lessens pain.

The question becomes “where does the pain come from and why does ‘clicking’ help? ”

In the 1970s I harvested a large number of cadaveric vertebrae. These vertebrae were stereo-radiographed, dissected, and after removal of soft tissue, using the stereo-radiograms, reassembled in the in vivo positions.

One purpose was to familiarize vertebral surgeons (myself included) with the large variation in the anatomy of the vertebral column.

In addition the facet joints anatomy and the mechanics of the facet joints in relation to orientation and instant locus of movement in to each other were explored. From that was extrapolated the relationship to the vectored loads on the intervertebral disc and the inter-segmental locus of movement.

In another study arthrograms were performed on a number of facet joints in these cadaveric spines with the soft tissues intact.  An example is below.

In the context of this paper, the most important finding of this research was the presence of an operculum in the facet joint capsule, which allowed passage through the capsule of a neurovascular bundle, into the intra-articular space.  Also demonstrated were features of the intra-articular fat within the capsule. [A later post will consider the function of the intra-articular fat.]

Much vertebral pain is clearly mechanical (because of its instant onset), and chiropractic (at least in its manipulative therapy guise) must provide a mechanical solution in order to cause the instant relief from pain. Therefore a mechanical sequence must be sought in any explanation of chiropractic benefit.

This paper postulates that the origin of some back pain (and the associated muscular spasm) is that the intra/extra-articular fat became entrapped in the operculum in the capsule.  This could explain the sudden onset of the pain. What the rotary manipulation does is to produce an intra-articular cavitation effect (and hence the click). Cavitation produces sudden changes of pressure within the joint capsule which forces the entrapped fat from its “locked” position in the operculum: Hence the instant relief.

Supporting this hypothesis was the beneficial treatment of “acute lumbar pain” by intra-articular injections of local anaesthetic and cortico steroid into the articular joints under radiological imaging, of which I performed many thousands, in the early 1970s.  The percentage of success was high, usually with an instant relief of pain comparable to that of successful chiropractic.  The long-term results appeared to be better than chiropractic.  A possible explanation for the latter is that the steroid produced an atrophy of the fat and hence less likelihood of future entrapment.  [Whether this atrophy caused some loss of proprioceptive capacity I don’t know, but it was one of my concerns at the time.]

A further benefit was the radiological demonstration of the vertebrae, a necessary precaution often not performed by the chiropractor. As a result of chiropractors missing these primary pathologies, and perhaps excessive forces, a number of patients were paralyzed or died when treated by chiropractic. This acted as a disincentive for some chiropractors who then replaced manipulative management with other techniques, such as “wedging”, or ventured into dietary supplements and other areas in order to continue their trade. Some claim or imply the special capacity to offer “holistic” treatment.


What is meant by this, and the reason that superiority of chiropractic over other forms of healthcare in this respect is far from clear.


[Documentation that injury can follow chiropractic has been requested. Under the search term “Chiropractic causing paralysis” Google provided 155,000 entries.

The papar is a comprehensive study.]