The back sometimes makes a sudden popping sound when twisting or stretching, and this may be accompanied by a feeling of comfort or lightness, leading to the belief that the popping is the cause of the improvement.
But what happens inside the back is more complicated than that, and the cracking sound alone does not necessarily tell us what has changed in the joints or vertebrae.
Many people associate the cracking sound with a feeling of improved mobility. When we sit for a long time, then change our position or stretch our back, we may hear a distinct sound that coincides with a feeling of relief.
Here, the brain may begin to associate the two events: stiffness, then cracking, then relief. With repeated experience, the sound becomes, for some people, a sign of successful movement or stretching.
Studies indicate that this belief is widespread. In one study of 100 people, 49% believed that the popping sound they heard during spinal manipulation meant a vertebra was being repositioned, while only 9% associated the sound with gas in the joint. In another question, 40% believed the popping sound was a sign that the treatment was successful.
These results suggest that sound may influence the way we interpret what is happening inside our bodies, even when it is not direct evidence of a particular change taking place.
Between the vertebrae are small joints called facet joints, which are synovial joints that help guide the movement of the spine. These joints contain synovial fluid that reduces friction and facilitates movement.
When joint surfaces move and separate rapidly, the pressure inside the joint can drop, creating a gas space. This phenomenon is known as "cavitation," and it is a common explanation for the popping sounds that come from joints.
Researchers were able to observe this process in finger joints using magnetic resonance imaging, where gas cavities appeared in conjunction with the separation of joint surfaces.
However, applying this explanation to the back is not so simple. The spine contains a large number of joints, muscles, ligaments, and other tissues, and a single movement can produce several sounds simultaneously. Therefore, the source of the cracking or what happened inside the back cannot be determined based on the sound alone.
There is nothing to indicate that the clicking sound itself means that a vertebra has moved from its place and then returned to it.
A systematic review published in 2022 investigated the role of cracking during chiropractic adjustments. The review included five studies on 303 adults, comparing movements that produced a cracking sound with silent ones.
The researchers found that the improvement in pain was similar in both cases, and that an increase in the number of cracks was not associated with an increase in the feeling of relief.
This does not mean that movement or therapy cannot help relieve the pain, but it does mean that the crackling sound itself does not seem to be a reliable indicator of successful treatment.
The improvement may be real, but the crackling is not necessarily the only reason behind it.
When we stretch after sitting for a long time, our posture changes, our muscles and joints move, and the load distribution on our spine is altered. Our attention also shifts from the feeling of stiffness to the movement itself, and the sound may give us a sense of accomplishment or reassurance.
Therefore, the cracking may just be part of a larger experience that includes movement, changing position, and a feeling of relaxation
Studies specifically investigating self-inflicted cracking during stretching are still limited, and there is insufficient evidence about the long-term effects of repeatedly attempting to crack one's own muscles.
If the popping occurs during a gentle movement and is not accompanied by pain or other symptoms, the sound alone usually does not indicate a problem.
However, it is best not to force the back into strong and repetitive movements in order to produce a cracking sound, or to press it hard to get this sound.
Most importantly, pay attention to any accompanying symptoms. If the cracking occurs after a severe injury, or is accompanied by severe or persistent pain, new weakness, numbness around the thighs, or changes in bladder or bowel control, a medical evaluation should be sought. Fever accompanying back pain also warrants medical attention.
