Actually, not all adjusting techniques produce the sound
associated with "popping knuckles." Some techniques
create no sound at all, some a little. Many techniques, however, do
create the sound of
a spinal "release." What causes this noise? The mystery
may have been solved by a British research team that took x-ray
movies of people "popping" their knuckles.
The sound appeared to be caused by gas rushing in to fill the
partial vacuum created when the joints were slightly separated.
