Why does the spine and other joints click and crack?
Good morning everyone,
We often get asked why do the joints crack and is it bad for you.
The cracking sound that is produced when the spine or the peripheral joints are adjusted come about from a sudden decrease in pressure inside the joint. Much like when you open a soda bottle the decrease in pressure causes the dissolved carbon dioxide gas in the solution to form bubbles. This occurs in the synovial fluid (joint fluid) as well, except nitrogen being the gas released. There is usually a ~20 minute latency period before you can produce another audible release in the same joint. I want to emphasize that the audible sound is not required for effective treatment and should be regarded as a byproduct of any joint adjustment/manipulation as (according to the current knowledge) the sound is not what produces the neurological effects we see when adjusting joints.
As I’m sure most of us have experienced some joint clicking or popping before I’ll cover some of the common reasons as to why this occurs:
- The peripheral joints, such as the shoulder, elbow and knee are complex structures with numerous ligaments (connecting bone to bone), tendons (connecting muscles to bones), fat pads and synovial bursae (a bit like two pieces of glad wrap with egg white in between to lessen the friction between tendons etc.) and other structures not to mention the nooks and crannies in the bones themselves. If the mechanical relationships between the muscles change (e.g. due to deconditioning/asymmetry between opposing muscle groups), the movements occurring in the joint will change and might lead to a tendon rubbing over a bony prominence and produce a snapping sound every time this happens.
- Sometimes after an injury a piece of the bone-cartilage complex might be broken off and remain in the joint cavity as a loose body or a “joint mouse” (the condition is called OCD and no, we’re not talking about mental illness but Osteochondritis Dissecans. Osteo refers to bone, chondro refers to the cartilage and dissecans refers to separation. A lesson in Latin!). Same applies to tearing of other intra-articular (inside the joint) structures such as the menisci in the knee. This will often lead to a feeling of locking or giving away of a joint combined with clicking or popping that may or may not be painful.
- Osteoarthritis (degeneration of the joint) can produce noisy joints as the joint surfaces degenerate. You might like to know that according to a recent study  published in Journal of American Board of Family Medicine knuckle cracking doesn’t seem to cause osteoarthritis. You can find the link to the the free article in references at the end of this entry.
And finally, the lovely spine! For those who haven’t read the previous entry on the basic anatomy of the spine and why we adjust I recommend having a look at it.
You might be surprised to hear that the 24 bones in the spine are exceptionally unstable. Some have described it as an inverted pyramid which without the constant neurological drive to the postural muscles would just collapse. It is quite remarkable when you think of the subconscious coordination required to smoothly move 24 individual bones/joint complexes harmoniously through smooth trajectories. That is, if the nervous system and the spine functions as it’s supposed to!
If there are joint fixations (i.e. dysfunctional spinal joints) then usually other parts of the spine start to compensate for the lack of movement by moving more than they’re supposed to (the brain likes to maintain full range of motion, even if it’s at the expense of other joints). As you can see, this leads to a situation where you have an area that is not doing what it’s supposed to, and consequently another area that is working overtime. Have you noticed that usually it’s the same area that always pops, not the whole spine?
People often describe it as “a need” to crack the neck or other part of the spine to “make it better”. However, over time the need to release the problematic area increases and begs the question, is the self-cracking really making anything better?
Perhaps the following explanation might give an insight to the mechanisms behind the need to crack the joints. As some parts in the spine become hypermobile, the muscles spanning the vertebrae (as well as the larger supporting muscles) have to work more in order to stabilize that area. The blood flow to the area, however, is maintained at a normal level because the increase in demand doesn’t exceed the need to increase metabolic support as e.g. vigorous exercising would. This leads to anaerobic energy production and subsequently increased lactic acid and H+ ion concentrations that irritate the tissues producing the tired and stiff feeling. The neurological effects of cracking the joint momentarily relaxes the muscles, increases the joint movement (albeit in a joint that is already moving too much) and produces relief for as long as the muscles start stiffening up again to protect excessive movement from occurring. Vicious cycle isn’t it?
Getting the spine moving like it should will not only lead to improved function of the nervous system but to help resolving the unwanted cracking as the healthy state of the spine is restored!
Hope you find this entry helpful! =)
Dr. Juho Hynninen, BChirSc, MChir
 deWeber K, Olszewski M, Ortolano R. Knuckle Cracking and Hand Osteoarthritis. Journal of the American Board of Family Medicine 24 (2): 169-174 (2011)