Do your ankles crack when you walk? Do your knees crack when you squat? Does your neck crackle when you turn your head? Hips pop when you stand from sitting?
Don’t worry, you’re totally normal. The cracking noise that comes from our joints is almost always from a cavitation in the joint. Cavitation means that a gas bubble forms in the joint as a way of equalising pressure in response to the rapid decrease in pressure as joint surfaces are separated. As the bubbles pop, the characteristic crack noise is heard, and then synovial fluid is redistributed in a greater amount of space. This means the pressure in the joint as a whole reduces, making it feel a bit looser. Over 15-30mins these gas bubbles are reabsorbed, and the crack can be performed again.
The cavitation of most joints in the body (we call it manipulation when done therapeutically) is absolutely safe when performed by a qualified therapist, but if the joint is cavitated habitually every 15-20mins this can stretch joint capsules, leading to laxity and possible instability. It will not cause osteoarthritis.
On a final note, cracking of the neck DOES carry some risk, even if performed by a qualified physiotherapist. The vertebral artery runs up to the back of the brain through the outside of the bones, and it is possible to cause compression or damage to this artery if manipulation is too energetic, or performed on osteoarthritic or osteoporotic necks. Damage to this artery can cause stroke, or even death. Your physiotherapist should inform you of these risks, and perform tests to check the likelihood of artery impingement. If you find yourself NEEDING to crack your neck for it to feel normal you probably have some weakness and instability, and need an exercise program – not repetitive self-manipulation.