Whether you are lying on the table of your osteopath or cracking your knuckles, you may ask yourself the same question: " What is this "crack" inside my joint?". No panic , no dismemberment to worry about!
For almost half a century this characteristic "crack/click/pop" has remained enigmatic. It was
mostly based on the theory of a gas bubble’ explosion. However a study using MRI to visualize the "crack" in real time demonstrated that this physiological phenomenon, obtained by separation of two articular surfaces close and opposite, is governed by the laws of tribonucleation .
The strange name of tribonucleation corresponds to a method which explains that two opposed surfaces resist until a critical point where they separate quickly. This separation causes the creation of cavities filled with gas that do not disappear instantaneously.
This process can be obtained in synovial joints. Our body has different types of joints (fibrous, cartilaginous and synovial). The synovial joint is the most mobile joint. It is characterized by a capsule creating a cavity filled with a liquid called synovial fluid. Synovial fluid is made from up to 15 % gas (80 % carbon dioxide) and the rest of liquid (water, minerals, small molecules, protein…) .
Indeed when you crack your knuckles or during an osteopathic manipulation, a pulling force is applied on the joint. But the separation of two articular surfaces aligned creates an adhesive force that resists the separation of the joints’ surfaces.
This creates a negative pressure within the joint. The decreasing pressure allied to speed enables gas to separate from the liquid, thereby creating a cavity.
In summary the quick separation of the joint surfaces leads to the creation of a cavity in the joint that causes the "crack".
This cavity remains after the "crack" and disappears once the joint’s strain is over. However a new joint noise can be achieved about twenty minutes after the first manipulation. Also the sound power of the “crack” depends on the size of the joint (the smaller it is the more noise it produces); the part of the body that is manipulated; and the activity before the manipulation.
Applied to the osteopathic field, these joint manipulations are called high-velocity techniques (in relation to the speed used to obtain the "crack "). They have different effects such as an immediate relief and a temporary restoration of joint mobility. However it appears that joint manipulation does not significantly modify the space between the joint surfaces.
Sometimes my osteopath can not "crack me": why?
There are various reasons why your osteopath can not make you crack :
The muscles are too contracted
This situation is very common, especially if you see your osteopath for the first time. The apprehension of the techniques, stress, poor hydration, and an inability to relax are reasons that lead to the contraction of the muscular system. This causes a strain over the joint that will prevent the surfaces’ separation.
The collateral ligaments are too short
This results in an inability to separate the articular surfaces efficiently
A hyperlaxity
This affects 4-13 % of the population ; patients have a non physiological flexibility characterized by a great range of motion.
The mobilization of the joint looks like it has already been manipulated
However if none of those factors is present, the absence of "crack" does not mean the technique is not effective. Indeed if the noise is an indicator of a physiological change within the joint, it is not so far proved to have a real therapeutic value. But the production of noise is very important for the patient as it will enable him to assume that the manipulation worked and unblocked the joint.
For those who hate the "crack" no panic! Your osteopath can use other techniques to relieve you and restore your joint mobility.
I hear a repetitive noise when I move my ankle/hip/shoulder : what is it?
The intraarticular “crack” has to be differentiate from the ligament or tendon’s noise. This latter is produced when a tensile structure rolls onto a bony surface.
A tendon connects a muscle to a bone meanwhile a ligament connects two bone surfaces to each other.
When moving a joint, there is:
A change in position of the tendon against the joint
Tension in the ligament to maintain the joint
This can result in a sound while climbing/going down the stairs, lifting the arm ...
Is it bad to crack to much?
There is a myth that cracking to much your knuckles would cause premature osteoarthritis. To end this myth, Donald Unger has conducted a study and cracked the fingers of his left hand on a daily basis for over 50 years! He published his study in 1998 and the results demonstrated that there was no alteration of the joints of his left hand in comparison to the right hand.
Its 36,500 " cracks " also have earned him the Nobel Prize for Medicine in 2009.
Other studies have highlighten the lack of correlation between the "crack" and the occurence of osteoarthritis in hands. However, current researches do not allow to really conclude.
According to DiGiovanna E. L ., recommendations are therefore not exceed 3 visits per week for high-velocity manipulation.
So let’s crack, clunk, pop !
Charlotte Mernier,
French Osteopath London
References :
Deweber, K., Olszewski, M., Ortolano, R. (2011) Knuckles cracking and hand osteoarthritis. Journal of the American Board of Family Medecine, 24(2), 169-174.
Evans, D.W., Breen, A.C. (2006) A biomechanical model for mechanically efficien cavitation production during spinal manipulation : prethrust position and the neutral zone, J Manipulative Physiol Ther, 29(1), 72-82.
Flynn, T.W., Fritz, J.M., Wainner, R.S., Whitman, J.M. (2003) The audible pop is not necessary for successful spinal High-velocity thrust manipulation in individuals with low back pain. Arch Phys Med Rehabil, 83, 1057-1060.
Harvard Medical School. Does knucles cracking cause arthritis ?, august 16th 2014, [Online] http://www.health.harvard.edu/healthbeat/does-knuckle-cracking-cause-arthritis (consulted the 21th january 2015).
Kawchuk, G.N., Fryer, J., Jaremko, J.L., Zeng, H., Rowe, L., Thompson, R. (2015) Real time visualizaton of joint cavitation. PLos ONE, 10(4).
Protopapas, M.G., Cymet, T.C. ( 2002) Joint crackind and popping : understanding noises that accompany articular release. The Journal of the American Osteopathic Association, 102(5), 283-287.
Unger, D.L. (1998) Does knuckles cracking lead to arthritis of the fingers ? Arthritis and Rheumatism, 41(5), 949-950.
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