Source
The physical mechanism is uncertain, and cracking may possibly arise from several different causes. Suggested causes include:
- Cavitation within the joint—small cavities of partial vacuum form in the fluid and then rapidly collapse, producing a sharp sound. This explains the popping that can occur in any joint, such as during spinal manipulation. Synovial fluid cavitation is the most likely theory and substantial evidence exists in support of it.
- Rapid stretching of ligaments.
- Intra-articular (within-joint) adhesions being broken.
Of these hypotheses, perhaps the most popular is cavitation. When a manipulation is performed, the applied force separates the articular surfaces of a fully encapsulated synovial joint, which in turn creates a reduction in pressure within the joint cavity. In this low-pressure environment, some of the gases that are dissolved in the synovial fluid (which are naturally found in all bodily fluids) leave the solution, making a bubble, or cavity, which rapidly collapses upon itself, resulting in a "clicking" sound. This process is known as cavitation. The contents of the resultant gas bubble are thought to be mainly carbon dioxide. The effects of this process will remain for a period of time known as the "refractory period", which can range from a few seconds to some hours while it is slowly reabsorbed back into the synovial fluid. There is some evidence that ligament laxity may be associated with an increased tendency to cavitate.
Read more about this topic: Cracking Joints
Famous quotes containing the word source:
“If, for instance, they have heard something from the postman, they attribute it to a semi-official statement; if they have fallen into conversation with a stranger at a bar, they can conscientiously describe him as a source that has hitherto proved unimpeachable. It is only when the journalist is reporting a whim of his own, and one to which he attaches minor importance, that he defines it as the opinion of well-informed circles.”
—Evelyn Waugh (19031966)
“Dear sensibility! source inexhausted of all thats precious in our joys, or costly in our sorrows!... eternal fountain of our feelings!tis here I trace theeand this is thy divinity which stirs within me ...all comes from thee, greatgreat SENSORIUM of the world!”
—Laurence Sterne (17131768)
“The act of birth is the first experience of anxiety, and thus the source and prototype of the affect of anxiety.”
—Sigmund Freud (18561939)