What is the popping sound that we hear with the chiropractic adjustment?
We all know the sound. Some people love it. Some people hate it. But what is it?
The noise is coming from bubbles of gas exiting the fluid in the joint, this process is called cavitation. In order to understand this let's look at the structure of the joint and we will also revisit some high school physics and chemistry.
A basic joint structure
Between two joints there is liquid called synovial fluid. The fluid is held in place by the joint capsule.
Some high school physics
When you add sugar to a cup of coffee, the sugar dissolves. Even though you’ve added something, the total volume stays the same as it was before. The sugar doesn’t make the coffee level rise but it's definitely in there!
This is like the experiment in high school science class where you dissolve salt in 10 ml of water. The water level doesn’t increase, but the weight does—because the salt is still there, just disolved in the water.
Gases can dissolve in liquids too. When a gas dissolves in a liquid, the solution stays the same size as the liquid was before the gas was added. But if you remove the gas again, you now have two separate things: the liquid and the gas, each with its own volume. So if you have a mixture of the liquid and the gas then the total size can change depending on how much of the gas is disolved in the liquid and how much of the gas is just hanging around as bubbles.
How this applies to our joint.
Inside the joint space is synovial fluid and carbon dioxide gas. Sometimes the gas is dissolved in the liquid and it takes up less space. Sometimes the gas is not dissolved but the gas bubbles are mixed with the liquid. In this scenario the liquid and gas mixture takes up more space. So the same joint is effectively bigger.
The process of the gas dissolving into the liquid usually happens quite slowly. The process of the gas exiting the liquid can happen very quickly with a pop; this is what happens during the chiropractic adjust.
When we perform the chiropractic adjustment we make a quick movement to make the joint bigger and you hear a little pop as the gas exits the synovial fluid and forms little bubbles.
This is the process called cavitation. All of that happens inside the joint itself.
Why is this good?
The bigger joint allows for better movement. In normal circumstances better movement means less pain and contributes to the longterm healing process.
The adjustment stimulates pain-reflief and muscle relaxation. You can read about the technical details on this website.
When performed correctly for the appropriate condition the chiropractic adjustment can form an important part of the treatment to decrease pain and improve function. As chiropractors we have trained and practiced for years in order to carry out the adjustments in a safe and purposeful manner.
Further reading
Why should I not 'crack' my own joints? - Blog post coming soon!
What training do chiropractors have? - Blog post coming soon! but for now see here
This website give some great scientific details on the the effect of the chiropractic adjustment
For appointment at Brussels Chiropractic clinic at Schuman you can phone 02 808 94 24 or follow the link below.
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