The Daily Mail reported that a 23-year-old woman suffered a paralyzing stroke after cracking her neck. What possibly explains this?
People crack their joints all the time, both intentionally and unintentionally. Personally, the euphoric sensation of cracking my knuckles (and neck) is something I can't resist. Other people pop knee joints when they bend down. It is often assumed that cracking joints is unhealthy and should be avoided, but there isn't any reason to believe this. We actually know what causes the popping sound: Air bubbles.
Most of the joints in our body are known as synovial joints. (See upper left image.) At a synovial joint, two cartilage-covered bones meet, and they are separated by a slippery synovial fluid that helps lubricate movement. (Without synovial fluid, the bones would grind against each other.)
When somebody cracks, say, a knuckle, the joint is being pulled. This causes a drop in pressure inside the joint and -- just like when opening a bottle of soda -- dissolved gas molecules can come out of solution, forming a bubble. The popping sound is the formation of that bubble. (In 2015, an MRI machine captured images of a joint cracking in real time.) It takes a while for the air bubble to redissolve, which is why a recently popped joint won't pop again for a few minutes.
Synovial joints are also found in the neck, and the exact same phenomenon is responsible for the sounds of a cracking neck. Arthritis or the movements of tendons and ligaments can also cause that sound. Can this cause a stroke?
No. Strokes ultimately have one of two causes: Blockage of a blood vessel (i.e., an ischemic stroke) or rupture of a blood vessel (i.e., a hemorrhagic stroke). Cracking joints will not cause either of those outcomes.
What explains, then, what happened to the young woman? It was probably a freak accident. It is known that high-velocity neck manipulation by chiropractors can, in rare cases, cause strokes. Rapidly twisting a person's neck can tear vertebral arteries, leading to internal bleeding. But this is extremely uncommon, and that a person could inadvertently do it to themselves, as apparently this young woman did, truly is a freak accident.
So, to you knuckle- and neck-poppers out there, feel free to pop away! You won't get a stroke, and your head (probably) won't fall off.