Cracking, popping and clicking joints are a common sound to most people. Some experience this noisiness more than others, but in most cases it isn’t painful.
What causes cracking in the joints?
There are several things that could be causing the noises coming from your joints:
Pockets of gas
This is the most common explanation for those pops and cracks that most people hear from joints such as the knees and shoulders and what happens when you deliberately crack your knuckles or neck, for example. The vast majority of the time these noises are completely painless and often there is little sensation at all to accompany the noise.
Previous explanations have centered around the noise being the bursting of a bubble of gas within the joint, but more recent research suggests that it could be just the opposite!
A team at the University of Alberta looked at knuckle joints using real-time MRI scans. They applied a traction force to observe what happens in the joint when a knuckle cracks. Rather than the bursting of a bubble (known as cavitation), a bubble of gas appeared to form.
Most joints in the body are “synovial” joints — meaning they are surrounded by a synovial membrane and are lubricated by synovial fluid that surrounds the joint surfaces within this membrane.
The explanation for this phenomenon goes that if you increase the space between two joint surfaces, there comes a point where there is no more fluid to fill the increasing space. At this point, it’s a bit like forming a vacuum and a cavity (bubble of gas) forms to fill the space, which is responsible for the sound.
While this has been shown in the knuckle joints, it has yet to be captured in larger synovial joints. It is, however, anticipated that the images would show the same bubble formation.