Anatomy of the Coccyx (Tailbone)

Anatomy of the Coccyx (Tailbone)

anatomical drawing of the spine
Fig 1: Spine
(larger view)

The coccyx is the very bottom portion of the spine. It represents a vestigial tail (hence the common term "tailbone") and consists of three or more very small bones fused together. The coccyx is made up of between three and five separate or fused vertebrae.

While it was originally thought that the coccyx is always fused together (with no movement between the coccygeal vertebrae), it is now known that the entire coccyx is not one solid bone but often there is some limited movement between the bones permitted by the fibrous joints and ligaments.

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The coccyx articulates with the sacrum through a vestigial disc, and is also connected to the sacrum with ligaments (see Figure 1). There is very limited movement between the coccyx and the sacrum.

Why Do More Coccyx Injuries Occur in Women Than Men?

The majority of coccyx injuries occur in women because:

  • The women's coccyx is rotated, leaving it more exposed to injury
  • Women have a broader pelvis, which means that sitting places pressure on their coccyx (male anatomy causes them to sit without much pressure on the coccyx)
  • Childbirth is a common cause of the condition.
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