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Lateral head of gastrocnemius muscle

The gastrocnemius muscle is a large, two-headed superficial calf muscle forming part of the triceps surae along with the soleus. The lateral head originates from the posterior aspect of the femur, above the lateral condyle. It descends with its medial counterpart to form the bulk of the calf and merges into the Achilles tendon.

The lateral head plays a vital role in powerful plantarflexion of the ankle and contributes to knee flexion. It is especially important in explosive movements like sprinting and jumping. Clinically, it is frequently involved in calf muscle injuries (such as “tennis leg”) and may be a site of myotendinous tears or tumors.

Synonyms

  • Gastrocnemius lateralis

  • Lateral calf muscle head

  • External head of gastrocnemius

Origin and Insertion

  • Origin: Lateral aspect of the lateral condyle of the femur and adjacent supracondylar area

  • Course: Fibers run downward and medially, forming the prominent bulge of the lateral calf; the belly merges with the medial head at the mid-calf level

  • Insertion: Both heads unite to form a common tendon that blends into the Achilles tendon, inserting onto the posterior surface of the calcaneus

Nerve Supply

  • Tibial nerve (S1–S2)

Arterial Supply

  • Sural branches of the popliteal artery

  • Contributions from posterior tibial artery and peroneal (fibular) artery branches

Venous Drainage

  • Small saphenous vein (superficial drainage)

  • Muscular venous branches drain into popliteal vein

Function

  • Ankle joint: Powerful plantarflexion of the foot

  • Knee joint: Assists in flexion of the leg

  • Stabilizes the knee during weight bearing

  • Provides explosive power in running, jumping, and climbing

  • Plays a role in venous return from the lower limb via muscle pump action

MRI Appearance

T1-weighted images:

  • Normal muscle: low-to-intermediate signal intensity

  • Fat between fibers and surrounding tissues: bright

  • Fatty degeneration or atrophy increases T1 signal intensity

T2-weighted images:

  • Normal muscle: low-to-intermediate signal intensity

  • Acute strain, edema, or tear: bright hyperintense regions

  • Chronic scarring: persistently dark signal bands

STIR (Short Tau Inversion Recovery):

  • Normal muscle: low-to-intermediate signal

  • Pathology (tear, strain, myositis, abscess): bright hyperintensity

Proton Density Fat-Saturated (PD FS):

  • Normal muscle: low-to-intermediate signal

  • Strains or myotendinous tears: bright signal areas, especially at lateral myotendinous junction

T1 Fat-Sat Post-Contrast:

  • Normal muscle: mild homogeneous enhancement

  • Inflammation, tumor, or infection: heterogeneous or nodular enhancement

  • Abscess or large tear with hematoma: rim enhancement with non-enhancing center

CT Appearance

Non-Contrast CT:

  • Muscle appears as homogeneous soft tissue density

  • Fat planes around it provide clear delineation from adjacent soleus and medial head

  • Acute hematoma: hyperdense

  • Chronic fatty degeneration: low attenuation streaks

Post-Contrast CT:

  • Normal muscle: mild homogeneous enhancement

  • Pathology (infection, tumor, inflammation): irregular or intense enhancement

  • Abscess: rim-enhancing lesion with central hypodensity

  • Myotendinous tear: focal hypodensity with surrounding fat stranding or fluid

MRI image

Gastrocnemius muscle (lateral head) anatomy image MRI 3T

MRI image

Gastrocnemius muscle (lateral head) anatomy image

CT image

Lateral head of gastrocnemius muscle ct axial image