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Medial head of gastrocnemius muscle

The medial head of the gastrocnemius is one of the two large superficial heads of the gastrocnemius muscle, the major calf muscle forming part of the triceps surae along with the lateral head of gastrocnemius and soleus. It arises above the medial condyle of the femur and contributes significantly to the rounded contour of the calf. The muscle crosses both the knee and ankle joints, making it a powerful plantar flexor and weak knee flexor.

It plays a key role in gait, jumping, and propulsion. Clinically, it is a common site of muscle tears (“tennis leg”), strains, and myotendinous injuries.

Synonyms

  • Medial gastrocnemius head

  • Inner head of gastrocnemius

  • Part of triceps surae

Origin and Insertion

  • Origin:

    • Posterior surface of the medial condyle of the femur and adjacent supracondylar area

  • Course:

    • Fibers descend posteriorly, forming a fusiform muscle belly that joins with the lateral head of gastrocnemius

    • Both heads unite into a common tendon, which merges with the soleus tendon to form the Achilles tendon

  • Insertion:

    • Posterior surface of the calcaneus (heel bone) via the Achilles tendon

Nerve Supply

  • Tibial nerve (S1–S2 roots)

Arterial Supply

  • Sural arteries (branches of popliteal artery)

  • Additional supply from posterior tibial and peroneal arteries

Venous Drainage

  • Sural veins and posterior tibial veins → popliteal vein

Function

  • Plantar flexion of the foot at the ankle joint (primary action)

  • Flexion of the leg at the knee joint (secondary action)

  • Provides propulsion in walking, running, and jumping

  • Assists in maintaining upright posture by stabilizing ankle and knee joints

  • Important in energy storage and release during athletic movement

MRI Appearance

T1-weighted images:

  • Muscle shows low-to-intermediate signal intensity

  • Fat within fascial planes appears bright

  • Fatty degeneration (chronic injury/atrophy) shows increased signal intensity

T2-weighted images:

  • Normal muscle: low-to-intermediate signal intensity

  • Acute strain, edema, or tear: bright hyperintense signal in myotendinous junction or muscle belly

STIR (Short Tau Inversion Recovery):

  • Normal muscle shows low-to-intermediate signal

  • Edema, strain, or hematoma: bright hyperintensity, very sensitive for acute injury

Proton Density Fat-Saturated (PD FS):

  • Normal muscle: low-to-intermediate signal

  • Partial tears, edema, or strain: bright hyperintense signal, excellent for defining lesion extent

T1 Fat-Sat Post-Contrast:

  • Normal muscle: mild, homogeneous enhancement

  • Myositis, tumor, or abscess: heterogeneous or nodular enhancement

  • Muscle tear with hematoma: peripheral enhancement with central non-enhancing fluid/blood

CT Appearance

Non-Contrast CT:

  • Muscle shows homogeneous soft tissue density

  • Hematoma: localized hyperdense region acutely, hypodense chronically

  • Fatty degeneration: low-attenuation streaks within muscle

Post-Contrast CT:

  • Normal muscle: mild, uniform enhancement

  • Inflammatory or neoplastic processes: irregular, heterogeneous enhancement

  • Abscess or chronic hematoma: rim enhancement with central low density

  • Fat stranding may be seen with myositis or trauma

MRI image

Gastrocnemius muscle (medial head ) anatomy image MRI 3T

MRI image

Gastrocnemius muscle (medial head ) anatomy image

CT image

Medial head of gastrocnemius muscle ct axial image