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Coccyx: anatomy, location and function

The coccyx is the small triangular bone at the bottom of the vertebral column. It anchors part of gluteus maximus, the coccygeus and levator ani muscles of the pelvic floor and the anococcygeal ligament, and shares weight when sitting back.

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Highlighted in the model: Coccyx. Click any part to read about it, or switch off “Highlight topic” to see the whole body. Use Male / Female to switch bodies. 3D data: BodyParts3D, © The Database Center for Life Science; knee ligaments, menisci, tonsils, palate and parotid glands from the Human Reference Atlas Visible Human Male model and female parts from its Visible Human Female model (HuBMAP / NIH); lung lobes built from the BodyParts3D chest; all CC BY 4.0; meshes simplified and recoloured. The female body shares the male skeleton, muscles and organs except its pelvis, reproductive organs, breasts, bladder, urethra and skin.

Coccyx at a glance

Also called
Tailbone
What it is
The coccyx is the small triangular bone at the bottom of the vertebral column.
Location
It lies below the sacrum, joined to it at the sacrococcygeal joint, at the back of the pelvic outlet.
Function
It anchors part of gluteus maximus, the coccygeus and levator ani muscles of the pelvic floor and the anococcygeal ligament, and shares weight when sitting back.
Body system
Skeletal · single, midline structure · female body
FMA ID
FMA20229 (Foundational Model of Anatomy)

Key facts

  • It is usually formed by four fused coccygeal vertebrae, though three to five occur.
  • Its tip is one end of the anteroposterior diameter of the pelvic outlet.
  • It can move slightly backward during childbirth, which widens the outlet.

Clinical relevance

Coccydynia (tailbone pain) is more common in women and often follows a fall or childbirth.

Structures next to the coccyx

The nearest named structures in the 3D model, measured from the centre of each part:

References

  1. Foundational Model of Anatomy: Coccyx (FMA20229). EMBL-EBI Ontology Lookup Service.
  2. OpenStax. Anatomy and Physiology 2e, §8.3 The Pelvic Girdle and Pelvis. Rice University, 2022.
  3. Mitsuhashi N. et al. (2009). BodyParts3D: 3D structure database for anatomical concepts. Nucleic Acids Research 37, D782–D785. Data © The Database Center for Life Science, CC BY 4.0.
  4. Browne K., Schlehlein H. 3D Reference Organ Set for United, Female (Visible Human Female). Human Reference Atlas 3D Reference Object Library, HuBMAP / NIH. Data from the NLM Visible Human Project. CC BY 4.0.

Related anatomy

Explore the whole body in the interactive 3D human anatomy model, or browse the A–Z list of human structures.