That Click from Your Back: “Joint Cracking” Mystery Solved

Cracking Your Fingers
Where Does The Click Sound Come From?

Ever wondered where the popping sound or cracking your back noise comes from? When a chiropractor does a spinal manipulation do you hear your spinal joints click? Do you click your fingers or knuckles because it feels good, but wondered what makes the popping sound in finger joints?

Today I want to explain where the “click, pop, snap, or cracking” sound can come from when clicking your back or fingers.

Cracking Your Joints

It is a common question I get as a chiropractor “What causes the popping sound in my back?”. Most people have heard that it is “air bubbles” popping in the joint. Some people are also worried bones may be breaking causing the noise. Well lets look more closely at the source of the joint cracking noise.

You finger and back (spinal) joints are called diarthrodial joints. This means that there are two bones connecting to one another at a joint. Each bony surface is covered in cartilage and there is a fluid in the joint (synovial fluid) with a capsule keeping the fluid inside.

You could imagine our spinal joints and knuckles are like any mechanical joint you can see bending and moving. Some joints can move in lots of directions whilst others only backward and forwards.

So where does that cracking joint sound come from inside then? Well a joint cracking noise comes from the synovial fluid. To be more specific it comes from the air bubbles (gas) in the synovial fluid. The air bubbles in the bony joint are made up different gases, mainly of carbon dioxide then nitrogen and oxygen. This joint gas then goes through the cavitation process to give you the click noise. The joint gasses make up about 15% of the joint volume and is about 80% carbon dioxide. I will explain the joint cavitation process below.

The Joint Cavitation Process

When a back joint or knuckles “clicks” then a cavitation has mostly likely happened. Chiropractors call a joint cavitation from spinal manipulation an “audible release”. A joint cavitation is created by the following process:

  1. You place the joint in a certain position. This is usually at the end range of movement of a joint.
  2. When you then push or pull the joint in this end range position. You may hear the popping sound.
  3. The reason that joints “pops” is that the pressure drops within the synovial fluid that lubricates the joint. This drop in joint volume pressure allows a gas bubble to form within the joint.
  4. The air bubble pushes on the joint ligaments and other surrounding structures forcing them to ‘pop’ outwards, producing the first of the possible two noises that you hear when you click your back or knuckles.
  5. The pressure in the joint then increases, causing the  air bubble to implode. This implosion will produce shockwaves and pull the joint ligaments inwards. This is what you hear as the cracking, popping, clicking or snapping sound from the joint.

FAQ about Cracking Joints

Here are some of the the frequently asked questions I then get asked after the “What causes the cracking noise” question

1. Is it Good or Bad to Crack your Knuckles?

The answer is Yes and No.

Yes, because cracking your knuckles frequently and habitually can weaken your grip strength. It also annoys parents, teachers and work colleagues who have to listen you popping your fingers all day :)

No, beacuse cracking your knuckles will not cause arthritis or big knuckles when your older. Donald Unger performed a study on himself. Donald wrote in his paper “Does Knuckle Cracking Lead to Arthritis of the Fingers?” for Arthritis & Rheumatism 1998 that after cracking his knuckles on his left hand for 50 years the left hand knuckles and fingers didn’t have more arthritis than the right hand.

2. Is it Good or Bad to Crack Your Back?

Again the answer is Yes and No.

Yes, because there are times when clicking your own back will feel needed to release pressure when moving.

No, if you are trying to crack your back often and it becomes a daily habit. This is a common one for especially chronic neck ache and low back pain sufferers. I’m sure you know the person rolling in bed to get that click sound or sitting in their chair pushing on their chin or rolling their neck to get a crack out the joint to relieve the pressure. What could be happening here is loosening the supporting ligaments and causing muscles to spasm around the joint to act like the supporting ligaments. This then feels like neck tension again which you try ‘pop’ again and again only making things worse.

3. Does Clicking my Joints Cause Arthritis?

No. As with the worry about knuckle cracking arthritis don’t worry about cracking a joint causing arthritis. Chiropractic manipulation of your spine won’t cause arthritis.

4. Why Does it Feel so Good to Crack Your Back?

When a joint ‘cracks’ you have changed the pressure in the joint. You have also stimulated the mechanoreceptors in the joint capsule. These mechanoreceptors sense the change at the joint and can rely information through the nervous system. This new information in the nervous system can help relax the surrounding muscles. This is why it then makes you feel good to crack your back.

5. My Neck Makes a Grinding Noises When I Move It

There are other sources for the noises you may hear when you move a joint. This is usually noticed by people when moving their necks. The other causes for joint sounds are:

  • Tendons moving over bones
  • Arthritic changes in the joint

If the joint keeps making a sound with repetitive movements then it is not a joint cavitation process as mentioned above. It takes time (approximately 20min) for the air bubble to enter the synovial fluid again.

I hope you have learnt a bit more about where the cracking your back or knuckles sound comes from and have cleared your mind of some of your clicking your back questions.