Pelvic outlet

Pelvic outlet
Pelvic outlet
	Diameters of inferior aperture of lesser pelvis (female)
	Muscles of the female perineum
Details
Identifiers
Latin	apertura pelvis inferior
TA98	A02.5.02.009
TA2	1290
FMA	17273
	Anatomical terms of bone [ edit on Wikidata]

Last updated November 11, 2025

The lower circumference of the lesser pelvis is very irregular; the space enclosed by it is named the inferior aperture or pelvic outlet. It is an important component of pelvimetry.

Boundaries

It has the following boundaries:

anteriorly: the pubic arch
laterally: the ischial tuberosities
posterolaterally: the inferior margin of the sacrotuberous ligament
posteriorly: the anterior border of the middle of the coccyx.^[1]

Notches

These eminences are separated by three notches:

one in front, the pubic arch, formed by the convergence of the inferior rami of the ischium and pubis on either side.
The other notches, one on either side, are formed by the sacrum and coccyx behind, the ischium in front, and the ilium above; they are called the sciatic notches; in the natural state they are converted into foramina by the sacrotuberous and sacrospinous ligaments.

In situ

When the ligaments are in situ, the inferior aperture of the pelvis is lozenge-shaped, bounded as follows:

in front, by the pubic arcuate ligament and the inferior rami of the pubes and ischia
laterally, by the ischial tuberosities
behind, by the sacrotuberous ligaments and the tip of the coccyx.

Additional images

Articulations of pelvis. Anterior view.
Articulations of pelvis. Posterior view.
Low-dose CT scan of sagittal pelvic outlet diameter as part of pelvimetry
Intertuberous diameter, as a measure of the transverse measure of the pelvic outlet

References

↑ Sara Paterson-Brown, Phillip Bennett, Catherine Williamson (2010). Basic Science in Obstetrics and Gynaecology (Fourth Edition) - Obstetric pelvic definitions and dimensions. Elsevier Ltd. ISBN 978-0-443-10281-3.{{cite book}}: CS1 maint: multiple names: authors list (link)

External links

pelvis at The Anatomy Lesson by Wesley Norman (Georgetown University) ( medialpelvissmall , malepelvissagittalinlet&outletsml )

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[1] Sara Paterson-Brown, Phillip Bennett, Catherine Williamson (2010). Basic Science in Obstetrics and Gynaecology (Fourth Edition) - Obstetric pelvic definitions and dimensions. Elsevier Ltd. ISBN 978-0-443-10281-3.{{cite book}}: CS1 maint: multiple names: authors list (link)

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