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Understanding the Pelvis: Anatomy, Function, and Common Conditions

The pelvis is a basin-shaped bony ring forming the base of the spine and connecting the axial skeleton to the lower limbs. It protects viscera, transmits weight, and enables locomotion.

Bony Anatomy (4 Fused Bones in Adult)

  • Two hip bones (os coxae): Each formed by fusion of ilium, ischium, pubis
  • Sacrum: 5 fused vertebrae (S1–S5); triangular, posterior
  • Coccyx: 3–5 fused rudimentary vertebrae; tailbone

Key Joints and Landmarks

  • Sacroiliac (SI) joints: Sacrum-ilium; weight transfer, limited mobility
  • Pubic symphysis: Fibrocartilaginous joint anteriorly
  • Acetabulum: Hip socket (ilium/ischium/pubis fusion site)
  • Obturator foramen: Large opening (nerve/vessel passage)
  • Pelvic inlet/outlet: Obstetric significance

Sex Differences

FeatureFemale (Gynecoid)Male (Android)
Inlet shapeOval/roundHeart-shaped
Subpubic angle>90°<90°
SacrumWider, shorter, less curvedNarrower, longer, more curved
Ischial spinesBlunt, wide apartSharp, closer
FunctionChildbirth adaptedWeight-bearing optimized

Functions

  • Protects pelvic viscera (bladder, rectum, reproductive organs)
  • Transmits axial load to femoral heads (standing/walking)
  • Attachment for core, pelvic floor, hip, thigh muscles
  • Childbirth passage (female)

Common Clinical Conditions

  • Pelvic fractures: High-energy trauma (MVC, falls); fragility fractures in elderly; classification guides management
  • Pelvic girdle pain: SI joint dysfunction, pubic symphysis diastasis (pregnancy), myofascial
  • Pelvic organ prolapse (POP): Anterior (cystocele), apical (uterine/vault), posterior (rectocele); pelvic floor weakness
  • Endometriosis/adenomyosis: Chronic pelvic pain, dysmenorrhea, infertility
  • Chronic pelvic pain syndrome: Multifactorial (urologic, gynecologic, GI, musculoskeletal, neurologic)
  • Pelvic floor dysfunction: Incontinence, constipation, dyspareunia, vaginismus

When to Seek Care

Persistent pelvic pain, urinary/bowel symptoms, palpable bulge, sexual dysfunction, or post-traumatic concerns warrant evaluation by primary care, gynecology, urology, or pelvic floor PT.

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