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Gracilis muscle

The gracilis muscle is a long, thin, strap-like muscle of the medial thigh. It is the most superficial and medial of the adductor group. Despite being relatively weak compared to other adductors, it plays an important role in thigh adduction and knee flexion. Clinically, the gracilis is significant as a donor muscle in reconstructive surgery (free muscle transfer) and is frequently involved in sports-related groin strains.

Synonyms

  • Strap muscle of the thigh

  • Gracile muscle

  • Medial thigh adductor (gracilis)

Origin, Course, and Insertion

  • Origin: Arises from the inferior ramus of the pubis near the pubic symphysis

  • Course: The muscle descends vertically along the medial side of the thigh, forming a long slender band. It crosses the knee joint on the medial side.

  • Insertion: Inserts into the medial surface of the tibia, just below the medial condyle, as part of the pes anserinus along with sartorius and semitendinosus tendons.

Nerve Supply

  • Obturator nerve (anterior division, roots L2–L4)

Arterial Supply

  • Obturator artery

  • Medial circumflex femoral artery

  • Contributions from profunda femoris artery

Venous Drainage

  • Venous blood drains into the obturator vein, profunda femoris vein, and femoral vein

Function

  • Adduction of the thigh

  • Flexion of the leg at the knee joint

  • Assists in medial rotation of the tibia when the knee is flexed

  • Stabilizes the pelvis during locomotion

MRI Appearance

T1-weighted images:

  • Muscle shows low-to-intermediate signal intensity

  • Fatty infiltration or chronic changes may appear as bright areas

T2-weighted images:

  • Baseline low-to-intermediate signal

  • Edema, acute strain, or inflammation appear bright

STIR (Short Tau Inversion Recovery):

  • Normal muscle is low-to-intermediate signal

  • Pathological conditions (edema, tear, inflammation) show high bright signal intensity

Proton Density Fat-Sat (PD FS):

  • Normal muscle: low-to-intermediate signal intensity

  • Muscle injury, strain, or tendinopathy: localized bright signal

T1 Fat-Sat Post-Contrast:

  • Normal gracilis shows mild, homogeneous enhancement

  • Myositis or tumor shows heterogeneous or intense enhancement

  • Abscess or necrotic lesions show peripheral rim enhancement

CT Appearance

Non-Contrast CT:

  • Homogeneous soft tissue density muscle along medial thigh

  • Acute hematoma appears as hyperdense region

  • Chronic fatty degeneration may appear hypodense

Post-Contrast CT:

  • Normal muscle: mild homogeneous enhancement

  • Inflammatory or neoplastic processes: more intense or heterogeneous enhancement

  • Abscess or necrosis: rim enhancement with central low density

MRI image

Gracilis muscle MRI axial anatomy image-img-00000-00000

CT image

Gracilis muscle axial ct image 1

CT image

Gracilis muscle axial ct image

CT image

Gracilis muscle ct coronal

MRI image

Gracilis muscle sag cross sectional anatomy 3T radiology anatomy image-img-00000-00000

MRI image

Gracilis muscle mri image

MRI image

Gracilis muscle