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Pubic symphysis

The pubic symphysis is a secondary cartilaginous joint (symphysis) located between the left and right pubic bones at the anterior midline of the pelvis. It is composed of fibrocartilage and reinforced by surrounding ligaments, providing limited mobility while contributing to pelvic stability. The joint is clinically important in trauma, pregnancy, and sports-related groin injuries.

Synonyms

  • Symphysis pubis

  • Interpubic joint

  • Pubic joint

Location and Structure

  • Situated in the midline at the junction of the left and right superior pubic rami

  • Consists of:

    • Fibrocartilaginous interpubic disc: a wedge-shaped fibrocartilaginous structure uniting the bones

    • Articular surfaces: covered by thin layers of hyaline cartilage on each pubic bone

    • Superior pubic ligament: strong band across the top of the symphysis

    • Inferior (arcuate) pubic ligament: arch-shaped band at the lower border

  • Contains a small interpubic cleft, sometimes filled with fluid, especially in females

Relations

  • Anteriorly: Skin and subcutaneous tissue of the pubic region

  • Posteriorly: Bladder (in males), bladder and urethra (in females)

  • Superiorly: Rectus abdominis and pyramidalis muscles inserting at pubic crest

  • Inferiorly: Urogenital diaphragm and external genitalia structures

Function

  • Provides stability to the anterior pelvis by uniting the pubic bones

  • Absorbs compressive forces during walking, running, and weight-bearing

  • Allows slight movement (rotation and shear) to facilitate locomotion and childbirth

  • Acts as a shock absorber for stresses transmitted through pelvis and lower limbs

Clinical Significance

  • Pregnancy/childbirth: Hormonal changes increase laxity, leading to pubic symphysis widening

  • Symphysis pubis dysfunction (SPD): Painful condition due to excessive movement or instability

  • Athletic pubalgia/osteitis pubis: Common in athletes with repetitive pelvic stress (e.g., football, hockey, running)

  • Pelvic trauma: Pubic symphysis diastasis is an important marker of unstable pelvic ring injuries

  • Surgical landmark: Used in urologic and gynecologic approaches

MRI Appearance

T1-weighted images:

  • Fibrocartilaginous disc and ligaments appear as low signal intensity

  • Bone marrow of adjacent pubic bodies shows intermediate signal intensity

T2-weighted images:

  • Fibrocartilaginous disc and ligaments appear as low signal intensity

  • Inflammation, edema, or osteitis pubis show increased signal intensity

STIR (Short Tau Inversion Recovery):

  • Fibrocartilage and ligaments remain dark

  • Edema, inflammation, or marrow stress reaction appear as bright signal intensity

T1 Fat-Sat Post-Contrast:

  • Normal ligaments and disc show minimal enhancement

  • Pathology (inflammation, osteitis pubis, infection) shows focal or diffuse enhancement

CT Appearance

Non-Contrast CT:

  • Joint visible as a narrow space between pubic bones

  • Fibrocartilage appears as soft tissue density

  • Widening, calcification, or erosions can be detected

  • Fractures or diastasis appear clearly

Post-Contrast CT:

  • Limited use for the joint itself

  • Inflammation or infection may show surrounding soft tissue enhancement

  • Abscess formation or osteomyelitis shows rim enhancement with low-density center

MRI image

Pubic symphysis mri axial image MRI coronal anatomy image-img-00000-00000

MRI image

Pubic symphysis mri axial image

CT image

Pubic symphysis ct axial image MRI coronal anatomy image-img-00000-00000

CT image

Pubic symphysis ct coronal image MRI coronal anatomy image-img-00000-00000