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Transverse acetabular ligament

The transverse acetabular ligament is a strong, fibrous band of the hip joint that spans the acetabular notch, completing the inferior rim of the acetabulum. It converts the notch into a foramen through which blood vessels and nerves enter the joint. Structurally, it is continuous with the acetabular labrum and functions as an important stabilizing structure in weight-bearing and hip joint movement.

It is short but clinically significant because of its role in supporting the femoral head, maintaining joint stability, and transmitting neurovascular structures.

Synonyms

  • Acetabular notch ligament

  • Inferior acetabular ligament

  • Transverse ligament of the acetabulum

Attachments

  • Spans across the acetabular notch, attaching from one edge of the notch to the other

  • Forms the inferior border of the acetabulum in continuity with the acetabular labrum

Relations

  • Superior: Acetabular fossa and femoral head

  • Inferior: Ligament bridges over vessels and nerves passing into the acetabulum

  • Continuous with the acetabular labrum on both ends

  • Related to synovial membrane of the hip joint

Function

  • Completes the inferior acetabular rim, deepening the socket for the femoral head

  • Converts the acetabular notch into a foramen allowing passage of the acetabular branch of the obturator artery (ligamentum teres artery)

  • Provides passive stability to the hip joint during weight bearing and rotation

  • Supports load transmission across the inferior hip joint

Clinical Significance

  • May calcify or ossify with age, visible on imaging

  • Can be injured in hip dislocation or acetabular fractures

  • Important landmark during hip arthroscopy and arthroplasty

  • Contributes to vascular entry point of femoral head; disruption may compromise blood supply

  • Degeneration associated with hip osteoarthritis

MRI Appearance

T1-weighted images:

  • Appears as a low-signal intensity band across acetabular notch

  • Surrounded by bright fat and intermediate signal marrow

T2-weighted images:

  • Ligament remains dark (low signal)

  • Adjacent synovial fluid appears bright, giving contrast

  • Tears or degeneration may appear as focal increased signal

STIR (Short Tau Inversion Recovery):

  • Ligament remains dark

  • Edema or injury appears as bright hyperintensity around or within ligament

T1 Fat-Sat Post-Contrast:

  • Normal ligament shows no significant enhancement

  • Pathological changes (synovitis, inflammation, neoplasm) may show adjacent or focal enhancement

CT Appearance

Non-Contrast CT:

  • Ligament itself is usually not well defined (soft tissue density)

  • May be indirectly identified bridging acetabular notch

  • Calcification or ossification may appear as linear density across notch

Post-Contrast CT:

  • Normal ligament does not enhance significantly

  • Inflammation or tumor infiltration may cause focal soft tissue thickening or enhancement in acetabular notch region

MRI image

Transverse acetabular ligament MRI axial anatomy image-img-00000-00000

MRI image

Transverse acetabular ligament MRI axial anatomy image-img-00000-00000_00001

MRI image

Transverse acetabular ligament MRI coronal anatomy image-img-00000-00000_00001

CT image

Transverse acetabular ligament ct axial image