This topic is an interesting one because most people do not know what or where the sound comes from and if it’s a good or bad thing.
Many people “crack” their own joints instinctively by twisting or pulling the joint in a certain direction. It is not to be confused with other joint sounds such as “clicking”, “clunking” “snapping” “crunching” or “grating” which may indicate a mechanical abnormality inside or around the joint.
The sensation of release of pressure and freedom of motion afterward usually feels good. We can all relate to a person who says “I feel like it just needs to pop”. See the video link:
https://www.youtube.com/watch?v=0hmWiDTA-xE
The “pop” or “crack” is actually a phenomenon known as cavitation, whereby a small bubble of gas is formed and quickly collapses. It is again dissolved in the synovial fluid inside the joint cavity.
Most fluids contain some gas dissolved in them, and the fluid inside your joints is no different. It is formed because of a reduction of pressure inside the joint when the joint surfaces are separated creating a suction type or negative pressure. Remember Boyle’s law in chemistry at school?
The effect of this bubble formation, and sudden collapse, inside the joint cavity is improved range of movement and a feeling of looseness or freedom of motion. The perfect remedy for a stiff joint.
However, is it bad to keep doing it? The short answer is no, but in some instances increasing joint mobility is not desirable, for example in an already hypermobile individual. Also, the repetitive motion to create the cavitation may in itself cause stress to the surrounding tissues or other joints nearby.
In some cases an individual may obsessively crack their joints. Imagine someone who cracks their knuckles when under psychological stress or anxiety. They are likely doing no harm to their joints, but in this case the cause of the behavior is what really needs addressed.
