Sacrum - Articulations


The sacrum articulates with four bones:

  • the last lumbar vertebra above
  • the coccyx (tailbone) below
  • the illium portion of the hip bone on either side

Rotation of the sacrum forward a few degrees vis-à-vis the ilia is sometimes called "nutation" (from the Latin term nutatio which means "nodding"), and the reverse (posterior) motion "counter-nutation." In upright vertebrates, the sacrum is capable of slight independent movement along the sagittal plane. When you bend backward the top (base) of the sacrum moves forward relative to the ilium; when you bend forward the top moves back.

The sacrum is called so when referred to all of the parts combined. Its parts are called sacral vertebrae when referred individually.

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