Where the sacrum sits in the skeleton
The sacrum is a triangular bone below the fifth lumbar vertebra, formed from five vertebrae fused into one. It sits between the hip bones and forms the back of the pelvis. Four pairs of sacral foramina on its front and back carry the sacral nerves. Ear-shaped surfaces on each side meet the ilium at the sacroiliac joints, and its lower tip joins the coccyx. The front upper edge of the first sacral body is called the sacral promontory.
Frequently asked questions
Which part of the skeleton is the sacrum in?
The sacrum is one of the bones of the vertebral column. Seven cervical, twelve thoracic and five lumbar vertebrae and the sacrum are stacked to support the trunk and enclose the spinal cord.
How many vertebrae are there?
The spine has 24 separate vertebrae. From the top there are seven cervical (neck), twelve thoracic (upper back) and five lumbar (lower back) vertebrae, followed by the sacrum and the coccyx.
Which bones are above and below the sacrum?
Above the sacrum is the fifth lumbar vertebra (L5), and below it is the coccyx. On either side it joins the hip bones.
How many pairs of sacral foramina are there?
Four pairs on the front and four on the back. Branches of the sacral nerves come out through them.
Other bones of the vertebral column
- Atlas (C1)
- Axis (C2)
- Third cervical vertebra (C3)
- Fourth cervical vertebra (C4)
- Fifth cervical vertebra (C5)
- Sixth cervical vertebra (C6)
- Seventh cervical vertebra (C7)
- First thoracic vertebra (T1)
- Second thoracic vertebra (T2)
- Third thoracic vertebra (T3)
- Fourth thoracic vertebra (T4)
- Fifth thoracic vertebra (T5)
- Sixth thoracic vertebra (T6)
- Seventh thoracic vertebra (T7)
- Eighth thoracic vertebra (T8)
- Ninth thoracic vertebra (T9)
- Tenth thoracic vertebra (T10)
- Eleventh thoracic vertebra (T11)
- Twelfth thoracic vertebra (T12)
- First lumbar vertebra (L1)
- Second lumbar vertebra (L2)
- Third lumbar vertebra (L3)
- Fourth lumbar vertebra (L4)
- Fifth lumbar vertebra (L5)
Joints of the sacrum
Bone counts
By region
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