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The Bony Pelvis & Gender Differences in Pelvic Anatomy

Pelvic skeleton includes two hip bones, sacrum and coccyx.

The geometry of bony pelvis differs significantly between males and females – the phenomena caused by adaptation to the obstetric demands. Females have a relatively larger and rounder pelvic cavity, a shorter and more posteriorly projecting sacrum, a wider subpubic angle, and smaller acetabula with a larger distance between them1,2. It is, however, worth mentioning that in real-life, the gender dimorphism of the pelvis is not as evident as generally described3,4.

The images presented here demonstrates the classically dimorphic pelvises with the length dimensions based on multiple sources of evidence5–10. The range of reference values reflects rather "average," than "the normal" range, or, by use of statistical terms – rather 95% Confidence Interval, than the double Standard Deviation.

  • 1 Fischer B, Mitteroecker P. Allometry and sexual dimorphism in the human pelvis. Rosenberg KR, Desilva JM, eds. Anat Rec. 2017;300(4):698-705.
  • 2 Patriquin ML, Steyn M, Loth SR. Metric analysis of sex differences in South African black and white pelves. Forensic Science International. 2005;147(2-3):119-127.
  • 3 Delprete H. Pelvic inlet shape is not as dimorphic as previously suggested. Rosenberg KR, Desilva JM, eds. Anat Rec (Hoboken). 2017;300(4):706-715.
  • 4 Vacca E, Di Vella G. Metric characterization of the human coxal bone on a recent Italian sample and multivariate discriminant analysis to determine sex. Forensic Science International. 2012;222(1-3):401.
  • 5 Siccardi MA, Imonugo O, Valle C. Anatomy, abdomen and pelvis, pelvic inlet. January 2020.
  • 6 Salk I, Cetin A, Salk S, Cetin M. Pelvimetry by three-dimensional computed tomography in non-pregnant multiparous women who delivered vaginally. Pol J Radiol. 2016;81:219-227.
  • 7 Keller TM, Rake A, Michel SCA, et al. Obstetric MR pelvimetry: reference values and evaluation of inter- and intraobserver error and intraindividual variability. Radiology. 2003;227(1):37-43.
  • 8 Buli HC. Pelvimetry in obstetrics. Postgraduate Medical Journal. 1949;25(285):310-318.
  • 9 Liao KD, Yu YH, Li YG, et al. Three-dimensional magnetic resonance pelvimetry – A new technique for evaluating the female pelvis in pregnancy. European Journal of Radiology. 2018;102:208-212.
  • 10 Kolesova O, Kolesovs A, Vetra J. Age-related trends of lesser pelvic architecture in females and males: a computed tomography pelvimetry study. Anat Cell Biol. 2017;50(4):265–10.
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    Icon of crossfade image Sexual dimorphism of pelvis. The frontal view
    Sex differences of pelvis. Frontal view Sexual dimorphism of pelvis. The frontal view
    Front view of the male and female pelvis.
    Note the gender difference in distance between two spina iliaca anterior superior (anterior spinal distance), the size of the acetabular fossa and the subpubic angle.
    The terminal line is a border between the greater and lesser pelvis.
    The list of terms: Pelvis major – Greater pelvis
    Pelvis minor – Lesser pelvis
    Linea terminalis – Terminal line
    Arcus pubis – Pubic arch
    Angulus subpubicus – Subpubic angle
    Crista iliaca – Iliac crest
    Distantia intercristalis – Intercristal distance
    Spina iliaca anterior superior – Anterior superior iliac spine
    Anterior spinal distance (iliac bi-spinous diameter)
    Icon of crossfade image Pelvic gender dimorphism. Top view
    Sex difference in pelvis. Top view
    Top aspect of the male and female pelvis.
    Note the pelvic inlet (apertura pelvis superior) – the upper opening of the lesser pelvis is bordered by the terminal line. The term conjugate apply to the pelvimetric distances in the median plane. The subtypes of conjugates are reviewed below.
    The list of terms: Apertura pelvis superior – Upper opening of lesser pelvis (pelvic inlet)
    Promontorium – Promontory of sacrum
    Ala ossis sacri – Ala sacralis
    Articulatio sacroiliaca – Sacroiliac joint
    Linea arcuata – Arcuate line
    Eminentia iliopubica – Iliopubic (iliopectineal) eminence
    Pecten ossis pubis – Pecten (pectineal line) of the pubis
    Symphisis pubica – Pubic symphysis
    Diameter conjugata – Conjugate diameter
    Diameter transversa – Transverse diameter
    Diameter obliqua – Oblique diameter
    Icon of crossfade image Markup for the bottom view of the human male and female pelvis
    Bottom view of the human male and female pelvis
    Bottom view of the male and female pelvis.
    The list of terms: Apertura pelvis inferior – Lower pelvic aperture (pelvic outlet)
    Coccyx
    Lig. sacrotuberale – Sacrotuberal ligament
    Tuber ischiadicum – Ischial tuberosity
    Arcus pubicus – Pubic arch
    Distantia interspinosa – Interspinous distance
    Diameter transversum – Transverse diameter of the pelvic outlet
    Conjugata recta – Straight conjugate
    Icon of crossfade image Markup for the pelvic axis
    Pelvic axis
    Medial view to the female pelvis. The left hip bone is removed to demonstrate the main pelvimetric conjugates used in obstetrics
    Note that anatomical straight conjugate is not particularly relevant. The sacrococcygeal joint is relatively elastic, adding some mobility to the coccygeal bone, so coccyx usually dislocates dorsally during childbirth*.
    The list of terms: Axis pelvis – Pelvic axis
    Conjugata anatotmica – Anatomic conjugate
    Conjugata vera (gynecologica) – Obstetrical conjugate
    Conjugata diagonalis – Diagonal conjugate
    Sagittal outlet diameter
    Conjugata recta – Straight conjugate
    Inclinatio pelvis – Pelvic inclination
  • * Wayne R. Cohen, Emanuel A. Friedman (2011). Labor and delivery care: a practical guide. John Wiley & Sons.
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    360° rotation of the male pelvis.
    First published: Apr/2020
    Last update: 12/Nov/2023