What is an Adjustment or Manipulation?
Updated: Nov 8, 2019
Hi everyone, in this week’s blog we are going to discuss what a ‘chiropractic adjustment’ or ‘physiotherapy manipulation’ is and explain what the ‘cracking’ noises that are created by these manoeuvrers are.
The definition of a spinal adjustment is “low-amplitude, high-velocity thrusts in which vertebrae are carried beyond the normal physiological range of movement without exceeding the boundaries of anatomic integrity”.
The normal range of movement of any synovial joint (active and passive) is known as the “physiological zone”.
At the end of this zone the joint meets a barrier known as the “physiological barrier”, and beyond this point is a secondary barrier, at the limit of the anatomical integrity of the joint.
The act of adjusting or manipulating a joint is controlled movement that forces the joint beyond the physiological barrier.
When applied a “cracking” sound can be elicited in this “paraphysiological space” where the movement is enough to force the joint beyond its normal physiological barrier but not exceed its anatomic integrity.
The anatomic integrity is bound by the joint capsule and ligaments, and movement beyond this barrier causes damage to those structure resulting in a joint sprain.
Adjustment and manipulation techniques are also known as “High-Velocity, Low Amplitude Thrust” (HVLAT) techniques. They can be applied to almost any joint in the body and are widely used in manual therapies to improve range of movement in a joint. They, almost, always produce a “cracking” noise, which is known as a cavitation event.
Common indications for the use of HVLAT techniques are “joint fixation”, “joint dysfunction” and “joint locking”, which essentially means reduced joint motion or a joint misalignment.
What is a cavitation?
When a manipulation is performed, the applied force separates the articular surfaces of a fully encapsulated synovial joint. This deforms the joint capsule and intra-articular tissues, which in turn creates a reduction in pressure within the joint cavity.
In this low-pressure environment, some of the gases that are dissolved in the synovial fluid (which are naturally found in all bodily fluids) form bubbles due to a reduction in pressure. As the gas bubbles expand, they pop, resulting in a 'clicking', ‘popping’ or ‘cracking’ sound.
The contents of this gas bubble are thought to be mainly carbon dioxide. The effects of this process will remain for a period of time termed the 'refractory period'. This can range from a few minutes to more than an hour, while the gas is slowly reabsorbed back into the synovial fluid.
There is some evidence that ligament laxity around the target joint is associated with an increased probability of cavitation, i.e. the laxer or looser a joint is, the more likely you are to achieve a cavitation event. Follow this link for a short facebook video demonstrating what happens when a joint ‘cracks’:
So that’s a brief overview of what an adjustment or manipulation is and an explanation of what causes the ‘cracking’ noise when this technique is applied.
In our clinical practice we find joint manipulation to be a very effective and safe technique, however it’s important to only have it performed by a qualified health professional as even in the hands of a trained person the joint can be forced beyond its anatomic integrity resulting in a joint sprain.
If you have any questions or comments regarding joint manipulation, please email us at firstname.lastname@example.org and we will be happy to answer them for you.
If you suffer with persistent back or neck stiffness, feel free to call us on (08) 9486 8653 and our therapists will be happy to chat with you about whether you may benefit from manipulative therapy.