Topics

Topic

design image
Superior gemellus muscle

The superior gemellus is a small, short muscle of the deep gluteal region. It belongs to the lateral rotator group of the hip and lies between the piriformis and obturator internus muscles. Despite its small size, it plays an important role in stabilizing the hip joint and assisting with external rotation. Its close anatomical relationship with the obturator internus makes it clinically and radiologically significant.

Synonyms

  • Upper twin muscle of the hip

  • Superior gemelli

  • Deep external hip rotator (superior gemellus)

Origin, Course, and Insertion

  • Origin: Arises from the ischial spine

  • Course: The muscle passes laterally, blending closely with the tendon of the obturator internus

  • Insertion: Attaches to the medial surface of the greater trochanter of the femur, via the conjoint tendon with the obturator internus

Nerve Supply

  • Nerve to obturator internus (L5, S1)

Arterial Supply

  • Inferior gluteal artery

  • Internal pudendal artery

  • Occasionally branches from medial circumflex femoral artery

Venous Drainage

  • Drains into the inferior gluteal vein and internal pudendal vein, then into internal iliac venous system

Function

  • External rotation of the thigh at the hip joint

  • Assists in abduction when the hip is flexed

  • Provides dynamic stabilization of the femoral head within the acetabulum

MRI Appearance

T1-weighted images:

  • Low-to-intermediate signal intensity

  • Fatty infiltration or chronic changes appear as areas of high signal intensity

T2-weighted images:

  • Low-to-intermediate signal baseline

  • Muscle strain, inflammation, or edema appears as bright signal intensity

STIR (Short Tau Inversion Recovery):

  • Normal muscle shows low-to-intermediate signal

  • Pathological states (strain, myositis) appear as bright signal

Proton Density Fat-Sat (PD FS):

  • Low-to-intermediate baseline signal

  • Pathology shows hyperintense foci or streaks

T1 Fat-Sat Post-Contrast:

  • Normal muscle enhances mildly and uniformly

  • Inflammation, tumor, or abscess shows variable, heterogeneous, or rim enhancement

CT Appearance

Non-Contrast CT:

  • Homogeneous soft tissue density

  • Acute hematoma may appear as localized high density within the muscle

  • Chronic degeneration may appear as areas of low attenuation

Post-Contrast CT:

  • Mild homogeneous enhancement in normal state

  • Inflammatory or neoplastic lesions enhance more intensely or heterogeneously

  • Abscess shows central low density with rim enhancement

MRI image

Superior gemellus muscle MRI axial anatomy image-img-00000-00000

CT image

Superior gemellus muscle CT AXIAL IMAGE

MRI image

Superior gemellus muscle MRI SAG anatomy image

MRI image

Superior gemellus muscle MRI coronal anatomy image