What happens when you crack your neck?
When you crack your neck, the popping sound usually comes from gas bubbles forming or collapsing in the fluid of the small joints in your spine as the joint is stretched.
The joints between the vertebrae in your neck, called facet joints, are surrounded by capsules filled with synovial fluid, which lubricates them. When you twist or stretch your neck, the pressure inside the joint drops quickly, and dissolved gases form a bubble, producing a pop. Studies using MRI have watched this happen in finger joints.
After cracking, it takes about 20 to 30 minutes before the same joint can crack again, as gases dissolve back into the fluid. Other sounds can come from tendons or ligaments moving over bones.
Is it harmful?
Occasional gentle neck cracking is generally considered harmless. However, forceful or frequent cracking may strain ligaments, and in rare cases, sudden forceful twisting has been linked to injuries to blood vessels in the neck. Anyone with neck pain, numbness or frequent urges to crack their neck should see a doctor.
Did You Know?
A doctor once cracked the knuckles of only one hand for 60 years to test whether it caused arthritis. He found no difference between his hands and won an Ig Nobel Prize in 2009.
This answer is general information, not medical advice. For a personal health question, talk to a doctor.