Editing Sacrum (section)

=== Articulations ===

The sacrum articulates with four bones:
* the last [[lumbar vertebra]] above
* the [[coccyx|coccyx (tailbone)]] below
* the [[Ilium (bone)|ilium]] portion of the [[hip bone]] on either side

Rotation of the sacrum superiorly and anteriorly whilst the coccyx moves posteriorly relative to the ilium is sometimes called "nutation" (from the Latin term [[wikt:nutatio|nutatio]] which means "nodding") and the reverse, postero-inferior motion of the sacrum relative to the ilium whilst the coccyx moves anteriorly, "counter-nutation".<ref>{{cite web|author=Joseph D. Kurnik, DC|url=http://www.chiroweb.com/archives/14/26/18.html|title=The AS Ilium Fixation, Nutation, and Respect|date=16 December 1996 }}</ref>
In upright vertebrates, the sacrum is capable of slight independent movement along the [[sagittal plane]]. On bending backward the top (base) of the sacrum moves forward relative to the ilium; on bending forward the top moves back.<ref>Maitland, J (2001). ''Spinal Manipulation Made Simple.'' Berkeley: North Atlantic Books, p.&nbsp;72.</ref>

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