Inferior Gemellus Muscle: Anatomy, Origin, Insertion, Function, Nerve Supply, MRI & CT Imaging

Topic

Inferior gemellus muscle

The inferior gemellus is a small, narrow muscle of the deep gluteal region. It is one of the short external rotators of the hip, working closely with the superior gemellus, obturator internus, and quadratus femoris. Despite its small size, it provides an important stabilizing role at the hip joint. In imaging, it is often assessed with the other deep gluteal muscles for evaluation of traumatic, inflammatory, or compressive syndromes.

Synonyms

Lower gemellus muscle
Inferior twin muscle
Deep lateral rotator of hip (inferior gemellus component)

Origin, Course, and Insertion

Origin: Arises from the upper part of the ischial tuberosity
Course: Fibers pass laterally, running almost horizontally across the posterior hip joint, lying inferior to the obturator internus tendon
Insertion: Attaches with the tendon of the obturator internus into the medial surface of the greater trochanter of the femur

Nerve Supply

Nerve to quadratus femoris (L4–S1)

Arterial Supply

Inferior gluteal artery
Medial circumflex femoral artery

Venous Drainage

Venous blood drains via venae comitantes of the inferior gluteal artery and femoral tributaries

Function

Lateral rotation of the thigh at the hip joint (when extended)
Abduction of the thigh (when flexed)
Stabilization of the femoral head within the acetabulum

MRI Appearance

T1-weighted images:

Muscle demonstrates low-to-intermediate signal intensity
Fat infiltration or chronic atrophy may show focal bright areas

T2-weighted images:

Muscle shows low-to-intermediate baseline signal intensity
Acute injury, edema, or inflammation appear as bright areas

STIR (Short Tau Inversion Recovery):

Normal muscle is low-to-intermediate signal
Pathological edema or strain shows bright hyperintensity

Proton Density Fat-Sat (PD FS):

Low-to-intermediate baseline signal
Muscle pathology, such as strain or tendinopathy, appears bright

T1 Fat-Sat Post-Contrast:

Normal muscle enhances mildly and homogeneously
Inflammatory or neoplastic lesions enhance more intensely or heterogeneously
Abscess shows peripheral rim enhancement

CT Appearance

Non-Contrast CT:

Appears as homogeneous soft tissue density in the deep gluteal space
Hematoma may appear as a hyperdense region
Fatty infiltration appears as areas of low attenuation

Post-Contrast CT:

Normal muscle enhances mildly and uniformly
Inflammatory or neoplastic lesions show irregular or more intense enhancement
Abscess shows rim enhancement with central low density

MRI image

CT image