|  Describing
the very first chiropractor adjustment in 1895 the founder of
chiropractic, Daniel D Palmer, wrote: “I replaced the displaced
fourth dorsal vertebra by one move”. The way he set about this
manoeuvre on the vertebrae was also described. Palmer “racked
it into position by using the spinious process as a lever.” He
emphasised that this was not haphazard, “there was nothing crude
about this adjustment; it was specific”.
Palmer’s adjustment was devised to move a vertebrae
back into alignment in a very specific and precise manner and
relied on applying pressure directly onto the vertebrae, unlike
the osteopaths of his day who used less direct leverage methods.
Early chiropractic was built up on the premise that displaced
spinal bones pressed on nerves causing pain elsewhere in the body
and disease of the organs the nerves supplied.
It was thought that bones quite readily moved
“out of place” and that the adjustment created a cracking sound
as it “popped them back in”. In fact, modern scientific understanding
has shown us that this isn’t quite the whole story.
How joints misalign or lock up
The function of a joint to move two
bones in relation to each other under muscular action. The muscles
act, when they receive impulses, through nerves that arise in
the spinal cord. The vertebral joints are like most other joints
in that they move within defined limits according to muscle activity
that is controlled by nerves leaving the spinal cord. Very often
injury, postural strains or other factors can irritate sensitive
joint capsules that retain the lubricant that bathes the joint.
 A
protective response is triggered that sends messages to muscles
that control the joint, causing one or more to contract. The effect
is to limit movement that might provoke more pain, sometimes drawing
the vertebra “out of alignment” in the process. This mechanism
can also be triggered by injury or strain to other parts of the
vertebral joint, such as its ligaments, disc, nerve, bone and
even its own muscles.
So any strain or injury to the joint or its associated
structures may cause a muscle contraction that locks the joint
either wholly or particularly. That locking can occur with the
joint in its neutral “aligned” position or, if muscles selectively
contract, out of its neutral position, so the bones appear “out
of alignment”.
The mechanism serves a purpose whilst the injured
tissue is healing by acting as nature’s own joint split. Anyone
who cuts a finger knows how rapidly the tissues heal, become pliable
again and return to full function. Unfortunately the spinal splinting
mechanism can sometimes go wrong and perpetuate itself long beyond
the time needed to repair the damaged tissue.
The contracting muscle can be so over effective
that it compresses its won blood supply, releasing acids that
build up and trigger nerve endings into sensing pain, inducing
a further protective spasm. A vicious cycle has been completed.
If a joint is locked for any length of time it
no longer exerts a stimulus upon its own tissues, such as its
ligament might be held in stretch whilst that on the opposite
side remains slack. In time they will respond by lengthening and
shortening respectively to balance the forces upon them, perpetuating
the “misaligned” appearance.
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 Each
area of the spine has certain characteristics that enable it to
perform a specific function. The five lumbar vertebrae of the
low back have a great capacity for bending forwards whilst the
seven cervical vertebrae in the neck allow for rotation. If a
set of joints in a region locks up then its neighbours must compensate
by increasing their own movement.
As they increase their range they become less stable and they
run the risk of strain or premature wear and tear, “osteoarthritis”.
A whole region can slowly get stiffer and stiffer in the process
so that bending the low back or reversing the car becomes a problem.
The process can precede imperceptibility over months or even years.
What the adjustment does
When the chiropractor adjusts a joint
he must first take up all the “slack” in the joint so as to control
the movement perfectly. There the patient must contribute by relaxing
completely to minimise any discomfort. The chiropractor aims to
induce a split-second stretch to the joint capsule and associated
muscles and tissue fibres. By taking up the slack the joint is
opened as far as it can voluntarily go, a point referred to by
chiropractors as the “elastic barrier of resistance”.
There is still ample room for the joint to move
within its anatomical range, but if the movement is a slow stretch
it triggers a natural resistance from the tissues of the joint.
The speed of the chiropractic adjustment is such that the joint
tissue resistance is not triggered and the elastic barrier is
overcome, often producing a joint “crack”.
The main effect of the rapid stretch is a neurological
response which creates a wave of relaxation within the joint tissues,
thereby restoring mobility. In cases where ligaments have physically
shortened, the joint will tend to stiffen up again, although usually
not to the same extent as before the adjustment. In time, with
repeated adjustment at regular intervals, short ligaments will
lengthen again, restoring full function to the joint.
 It
was once thought the joint crack was made by the bones as they
“popped back into place”. Another theory was that the noise came
from the ligaments as they slapped tissues on being fully stretched.
In the late sixties researchers at Leeds university showed that
the pop occurred within the fluids in the form of tiny bubbles
(anyone who saves wine from oxidation by using a bottle pump will
notice how bubbles form the wine if too much air is extracted).
As the vacuum increases within the joint fluids, the bubbles come
together until they form one sizable bubble. The next phase occurs
as the bubble bursts with a “pop”. All this happens painlessly
in a fraction of a split second.
Although it is an indication that a joint has
been adjusted, the “crack” is not essential to the success of
the adjustment, as it is the rapid stretch and not the bursting
bubble that induces tissue relaxation and increased mobility.
Indeed, chiropractors have devised numerous methods over the years
for restoring full mobility, not all of which require the mediation
of the classic chiropractic adjustment.
There are instances when the adjustment is not
called for, as Daniel palmer’s son, “B.J.”, recognised when he
wrote; “it is more important to know when not to adjust then when
to adjust”. In such cases chiropractors will use some of their
“non-force” techniques to restore movement and function to a faulty
joint.
Do not feel disappointed if your chiropractor
tells you your bone is not “out of place”. Excruciating pain can
still be caused by locked joints that are technically still in
alignment. If you do not hear your joints go “crack” when they
are treated do not feel cheated. The quickest way to full function
and painless relief may sometimes by a silent one.
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