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Ligamentum teres (ligament of the head of femur)

The ligamentum teres, or ligament of the head of the femur, is a triangular intra-articular ligament that connects the femoral head to the acetabulum. Though once considered vestigial, it is now recognized as an important stabilizer of the hip joint and a conduit for vascular supply during early life. It also contributes to proprioception and may become a source of hip pain when torn or inflamed.

Synonyms

  • Ligament of head of femur

  • Round ligament of femur

  • Ligamentum capitis femoris

Attachments

  • Acetabular attachment: Arises from the margins of the acetabular notch and the transverse acetabular ligament

  • Femoral attachment: Inserts into the fovea capitis femoris on the femoral head

Relations

  • Lies within the hip joint capsule, covered by synovium

  • Surrounded by synovial folds that carry small blood vessels

  • In proximity to the acetabular labrum and articular cartilage of femoral head

Function

  • Provides secondary stabilization of the hip joint, especially in flexion and external rotation

  • Acts as a conduit for blood vessels to the femoral head in children (acetabular branch of obturator artery)

  • Contains mechanoreceptors and nociceptors, contributing to proprioception and pain sensation

  • Plays a role in hip joint kinematics and limiting extreme ranges of motion

Clinical Significance

  • Tears: Common in athletes; may cause hip pain, clicking, or instability

  • Hip dislocation: Ligament can be torn, stretched, or avulsed

  • Vascular role: In children, it carries important vessels that contribute to femoral head vascularity; in adults, its vascular role diminishes but remains clinically relevant

  • Arthroscopy: Frequently evaluated during hip arthroscopy for labral tears and instability

  • Degeneration: May calcify or become hypertrophic in chronic hip disease

MRI Appearance

T1-weighted images:

  • Appears as a low-signal (dark) band from acetabulum to fovea capitis

  • Surrounded by bright joint fat and intermediate cartilage signal

T2-weighted images:

  • Normally low signal

  • Tears or degeneration: focal or diffuse hyperintensity within ligament

STIR (Short Tau Inversion Recovery):

  • Ligament remains dark in normal state

  • Pathology (tear, edema, inflammation): bright hyperintensity

T1 Fat-Sat Post-Contrast:

  • Normal ligament: minimal or no enhancement

  • Inflammation or partial tear: mild enhancement

  • Synovitis or arthropathy involving ligament: enhancing synovial tissue around ligament

CT Appearance

Non-Contrast CT:

  • May appear as a thin soft tissue density within hip joint

  • Calcification in chronic degeneration can be seen as high-density foci

Post-Contrast CT:

  • Ligament itself does not enhance significantly

  • Surrounding synovium or joint effusion may enhance in inflammatory or infectious processes

  • Tears are inferred indirectly by effusion, displaced fragments, or contrast outlining abnormal gap

MRI image

Ligamentum Teres (ligament of the head of femur) MRI coronal anatomy image-img-00000-00000

MRI image

Ligamentum Teres (ligament of the head of femur) MRI sag anatomy image-img-00000-00000

MRI image

Ligamentum Teres (ligament of the head of femur) MRI axial anatomy image-img-00000-00000

CT image

Ligamentum Teres (ligament of the head of femur) ct axial image

CT image

Zona orbicularis ligament CT axial anatomy image-img-00000-00000