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Vastus medialis muscle

The vastus medialis is one of the four muscles of the quadriceps femoris group, located in the anterior compartment of the thigh. It is situated medially and is easily visible on the anterior thigh surface. Its distal fibers form the vastus medialis obliquus (VMO), which plays a crucial role in stabilizing the patella. The muscle is important for knee extension, patellar alignment, and lower limb biomechanics, and is clinically significant in patellofemoral pain and knee surgery.

Synonyms

  • Vastus medialis obliquus (distal fibers)

  • Medial vastus muscle

  • Quadriceps medialis

Origin, Course, and Insertion

  • Origin:

    • Arises from the intertrochanteric line, pectineal line, linea aspera (medial lip), and medial supracondylar line of the femur

  • Course:

    • Fibers descend vertically along the medial thigh

    • The distal fibers, known as the vastus medialis obliquus, run obliquely and horizontally to insert into the patella

    • Lies medial to the rectus femoris and vastus intermedius, and lateral to the adductor group

  • Insertion:

    • Inserts into the medial border of the patella, and via the quadriceps tendon into the tibial tuberosity

Relations

  • Anteriorly: Subcutaneous tissue and skin of the anterior thigh

  • Posteriorly: Adductor magnus and adductor longus

  • Medially: Sartorius and adductor canal (with femoral vessels)

  • Laterally: Vastus intermedius and rectus femoris

Nerve Supply

  • Femoral nerve (L2–L4)

Arterial Supply

  • Femoral artery

  • Profunda femoris (deep femoral) artery

  • Descending genicular artery

Venous Drainage

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

Function

  • Extension of the leg at the knee joint

  • Vastus medialis obliquus (VMO) stabilizes the patella medially

  • Prevents lateral displacement of the patella during knee extension

  • Contributes to efficient gait and running mechanics

Clinical Significance

  • Weakness or atrophy is associated with patellofemoral pain syndrome

  • Plays a vital role in rehabilitation following knee injuries and surgeries

  • Important in ACL reconstruction rehab due to its role in patellar tracking

  • May be injured in anterior thigh trauma or compartment syndrome

MRI Appearance

T1-weighted images:

  • Muscle shows low-to-intermediate signal intensity

  • Chronic fatty infiltration appears as bright signal areas

T2-weighted images:

  • Muscle has low-to-intermediate baseline signal intensity

  • Acute edema, strain, or inflammation shows bright signal

STIR (Short Tau Inversion Recovery):

  • Normal signal is low-to-intermediate

  • Injury or inflammation appears as bright signal

Proton Density Fat-Sat (PD FS):

  • Normal muscle shows low-to-intermediate signal

  • Strain or tendinopathy appears as localized bright signal

T1 Fat-Sat Post-Contrast:

  • Normal muscle shows mild, uniform enhancement

  • Pathology demonstrates heterogeneous or rim enhancement

CT Appearance

Non-Contrast CT:

  • Muscle appears as homogeneous soft tissue density

  • Hematomas appear as localized hyperdense regions

  • Chronic fatty degeneration appears as low attenuation areas

Post-Contrast CT:

  • Normal muscle shows mild homogeneous enhancement

  • Inflammatory or neoplastic lesions show irregular or intense enhancement

  • Abscess appears as central low density with peripheral rim enhancement

CT image

Vastus medialis muscle CT coronal

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Vastus medialis muscle CT axial 1

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Vastus medialis muscle CT axial

MRI image

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MRI image

Vastus medialis muscle mri axial anatomy image-img-00000-00000_00001

MRI image

vastus medialis muscle image

MRI image

vastus medialis muscle mri axial image