• Question: why do our knuckles pop

    Asked by hannah B to Iain, Hayley on 25 Jun 2015.
    • Photo: Hayley Clissold

      Hayley Clissold answered on 25 Jun 2015:

      When we crack our knuckles, the space between our bones expands. This causes synovial fluid (a type of fluid found between joints) to fill in the gap that has been created. The movement of the synovial fluid into the gap causes a popping sound and that’s what we hear!

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