Often times with an adjustment, an audible ‘pop’ may be heard.
The ‘pop’ is a sound created as tiny nitrogen, oxygen, and carbon dioxide gas bubbles are formed within the joint and released.
A joint capsule surrounds most joints and that capsule contains a lubricating joint fluid so that your joints are able to glide smoothly. It is normal for these gas bubbles to form in the joint fluid, within the joint capsule, and create a popping sound as they are released.
The popping has nothing to due with bones cracking, should not be painful, does not cause arthritis, and does not cause your joints to enlarge.
Not all adjustments can be heard, and therefore the pop does not indicate a successful treatment. An adjustment can be very therapeutic and provide benefits regardless of popping or no popping.