Gastrocnemius
Introduction[edit | edit source]
Gastrocnemius muscle is the muscle which form the major bulk at the back of lower leg and is a very powerful muscle. It have 2 heads and runs from back of knee to the heel and is involved in standing, walking, running and jumping. This along with soleus and plantaris together forms the calf muscle or triceps surae.It is a two joint or biarticular muscle which is prone to spasm.Also there are sesamoid bones called "fabella" in the lateral head of gastrocnemius muscle
Anatomy[edit | edit source]
ORIGIN
It have 2 heads and the two heads unite into a broad aponeurosis which eventually unites with the deep tendon of the soleus to form the Achilles tendon at it insertion.
Medial head: from posterior nonarticular surface of medial femoral condyle
Lateral head: from lateral surface of femoral lateral condyle.
INSERTION
The middle 1/3 of the posterior calcaneal surface.
ACTION
Powerful plantarflexion at ankle joint.
Flexion at knee joint.
INNERVATION
Tibial nerve (S1,S2)
ARTERIAL SUPPLY
Each head supplied by a sural branch of the popliteal artery.
Clinical significance & Function[edit | edit source]
As gastrocnemius is strong plantarflexion but enter as stage of passive insufficiency during the completion or at full dorsiflexion of ankle joint and the knee is near it or in it full extension range. As the knee flexion increases (soleus become more active) and the ankle throught or in complete plantarflexion (hamstrings become more active) the muscle is in active insufficieny stage.In the seated calf raise (knees flexed to 90º), the gastrocs are virtually inactive while the load is borne almost entirely by the soleus. Gastrocnemius is active during the eccentric phase whereas the soleus is active during the concenctric phase.
The lateral and medial head of gastrocnemius muscle do not involve in the hip rotation but in and MRI study by Dr. Per Tesch (Sweden) suggests "toes in" activate both heads and "toes out" activate the medial head to a higher degree.
