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Vastus intermedius muscle

The vastus intermedius muscle is one of the four muscles of the quadriceps femoris group, located deep between the vastus lateralis and vastus medialis, and beneath the rectus femoris. It forms the central bulk of the anterior thigh and contributes significantly to knee extension. Its deep position makes it less palpable clinically, but it plays an important role in stabilizing the patella and is a common site for quadriceps tendon pathology and intramuscular injuries.

Synonyms

  • Quadriceps intermedius

  • Middle vastus of the thigh

  • Central quadriceps muscle

Origin and Insertion

  • Origin: Anterior and lateral surfaces of the shaft of the femur (upper two-thirds)

  • Course: Fibers run vertically downward beneath rectus femoris, fusing distally with other quadriceps components

  • Insertion: Quadriceps tendon → patella → tibial tuberosity via patellar ligament

Nerve Supply

  • Femoral nerve (L2–L4)

Arterial Supply

  • Lateral circumflex femoral artery

  • Deep femoral (profunda femoris) artery

  • Femoral artery muscular branches

Venous Drainage

  • Drains into venae comitantes of profunda femoris vein and femoral vein

Function

  • Primary extensor of the knee joint

  • Contributes to patellar stability via quadriceps tendon

  • Provides anterior support to the thigh and knee during gait and posture

MRI Appearance

T1-weighted images:

  • Normal muscle shows low-to-intermediate signal intensity

  • Intramuscular fat or chronic degeneration appears bright

T2-weighted images:

  • Normal muscle shows low-to-intermediate signal

  • Muscle strain, edema, or tear appears as bright hyperintensity, often at the myotendinous junction

STIR (Short Tau Inversion Recovery):

  • Normal muscle remains low-to-intermediate signal

  • Acute injury, inflammation, or edema: bright hyperintensity

Proton Density Fat-Saturated (PD FS):

  • Normal muscle: Intermediate signal

  • Pathology (strain, tendinopathy, or tear): bright signal intensity

T1 Fat-Sat Post-Contrast:

  • Normal muscle enhances mildly and homogeneously

  • Pathology (myositis, tumor, abscess): heterogeneous, focal, or rim enhancement depending on etiology

CT Appearance

Non-Contrast CT:

  • Muscle appears as a homogeneous soft tissue density in the anterior thigh

  • Fatty streaks or planes provide definition

  • Hematoma: hyperdense in acute stage; hypodense if chronic

Post-Contrast CT:

  • Normal muscle enhances mildly and uniformly

  • Abscess: rim enhancement with central low attenuation

  • Tumor or inflammatory infiltration: heterogeneous or irregular enhancement

  • Fat stranding may indicate acute inflammation or trauma

MRI images

Vastus intermedius muscle MRI axial anatomy image-img-00000-00000

MRI images

Vastus intermedius muscle MRI axial anatomy image-img-00000-00000_00001

MRI images

Vastus intermedius muscle MRI axial anatomy image-img-00000-00000_00002

CT image

Vastus intermedius muscle CT axial anatomy image-img-00000-00000