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:
“By poeticizing love, we imagine in those we love virtues that they often do not possess; this then becomes the source of constant mistakes and constant distress.”
—Anton Pavlovich Chekhov (1860–1904)
“The child knows only that he engages in play because it is enjoyable. He isn’t aware of his need to play—a need which has its source in the pressure of unsolved problems. Nor does he know that his pleasure in playing comes from a deep sense of well-being that is the direct result of feeling in control of things, in contrast to the rest of his life, which is managed by his parents or other adults.”
—Bruno Bettelheim (20th century)
“The act of birth is the first experience of anxiety, and thus the source and prototype of the affect of anxiety.”
—Sigmund Freud (1856–1939)