In 400 B．C., Hippocrates described combinations of spinal traction and manipulation. Spinal manipulation remains widely used today, with many patients with low back pain seeking this treatment. During this manipulation, a cracking sound is heard, which is now ascribed to cavitation, which is the formation of bubbles in a fluid when exposed to a drop in pressure. However, the origin of this sound remains enigmatic to the general population. This study evaluated beliefs regarding this sound.

Subjects were 60 individuals with, and 40 without, a history of spinal manipulation. All were interviewed during a face-to-face meeting. Data collected included demographics and medical history, including experience with spinal manipulation and beliefs regarding the cracking sounds heard during these procedures.

Of the respondents, 50% of those treated with spinal manipulation, and 48.3% of those who had not received that treatment, believed the sound was the result of the repositioning of the vertebrae. The second most common belief was that the sound was caused by friction between vertebrae. Only nine percent indicated that the sound was produced by a gas bubble within the joint. Overall 40% believed that the cracking sound was proof of a successful spinal manipulation.

This study found that most people have erroneous beliefs about the cracking sound heard during spinal manipulation.