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Sacrum
The sacrum (pronounced say-crum) is a large
triangle shaped bone in the lower part of the
spine. The sacrum consists of five vertebrae
(bones that form an opening in which the spinal
cord passes), known as S1 through S5. These
bones are originally separate, but join together
between ages 18 and 30, as if they were one
bone.
These bones decrease in size and thickness from the top part of the sacrum to the
bottom. The sacrum is a wide bone that is slightly curved and is pictured below.
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WHERE IS THE SACRUM?
The sacrum is wedged in between the center of the back and the coccyx (also known as
the tailbone). The coccyx is a beaked shaped bone that makes up part of the back of the
pelvis. The pelvis is a massive bone made of hip bones on each side and the front, while
the back part is made of the sacrum and the coccyx. The coccyx is below the sacrum.
The top part of the sacrum is joined to the fifth (lowest) lumbar vertebrae (see above for
definition). Lumbar means pertaining to the loin, part of the back between the lowest pair
of ribs of the thorax (chest) and the top of the pelvis. The sides of the sacrum are
connected to the ilium (the largest bone of the pelvis) by tissues known as sacroiliac
joints (sacro for sacrum; iliac for ilium).
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IS THE SACRUM STRONG?
The sacrum is a strong bone that is rarely
fractured. If you've fractured your sacrum, then
you have likely suffered a serious injury, such as
a fall or a powerful blow to the area.
IS THE SACRUM OF A WOMAN DIFFERENT
FROM THE SACRUM OF A MAN?
Yes. The sacrum is wider and shorter in women
compared to men.
WHAT ARE OTHER FORMS OF THE WORD "SACRUM"?
Sacral is an adjective that is commonly used to describe the area of the sacrum or one of the five nerves
(known as sacral nerves) that emerge from the sacrum. The plural of sacrum is sacra.
WHAT ELSE IS THE SACRUM KNOWN AS?
The sacrum is also known as the os sacrum, sacred bone, and the vertebra magna.
WHAT IS THE ORIGIN OF THE WORD "SACRUM"?
Sacrum comes from the Latin word "sacer" meaning "sacred." This is because the sacrum was
considered a sacred (highly valued; holy) bone. Specifically, it was believed that the sacrum could not be
destroyed and that it was the part of the body that would allow someone to rise from the dead.