Why Do My Knee’s ‘Crack’?

We are often asked by patients:” Why do my knees crack?” Or “what is making that noise when you click my back?” The crack you may here from your knees, or if you crack your knuckles (which does not cause arthritis by the way), or when your spine is manipulated, is essentially the same thing. It is what’s known as a cavitation. When a joint “cracks” the two surfaces that make up a fully encapsulated joint are momentarily separated. This creates a reduction in pressure within the joint and gases that arepopping joints naturally found within the synovial fluid (the fluid that helps lubricate the joint) form a bubble. This bubble pops/collapses resulting in the “cracking” sound.

Contrary to popular belief it is not the “crack” chiropractors aim to achieve when performing spinal manipulation. It is the separation of the joint surfaces that has the therapeutic value.

You may also experience “snapping” of joints; it is thought this noise comes from tendons “snapping” over other tissue such as bony prominences a because of minor adjustments in their gliding path.

All in all non-painful cracks, pops or snaps have not shown to be harmful. If however you are experience pain when your joints “cracks” or “pops” we would advise contacting the clinic to arrange an assessment by your chiropractor as this may suggest an underlying abnormality.

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