Quick Facts
Origin: Lateral and medial condyles of femur, lateral supracondylar line, and popliteal surface of femur.
Insertion: Posterior surface of calcaneus, via calcaneal tendon.
Action: Plantarflexes foot at ankle joint; flexes leg at knee joint.
Innervation: Tibial nerve (S1-S2).
Arterial Supply: Sural arteries.
Related parts of the anatomy
Origin
The gastrocnemius muscle consists of two heads:
- a medial head, which originates from the posterior aspect of the medial condyle of the femur and the lateral aspect of the popliteal surface of the femur;
- a lateral head, which originates from the lateral aspect of the lateral condyle of the femur and the inferior half of the lateral supracondylar line of the femur.
Insertion
The fibers of the medial and lateral heads of gastrocnemius travel inferiorly and converge with each other and with the fibers of the soleus muscle to form the calcaneal tendon, which inserts onto the posterior surface of the calcaneus.
Key Features & Anatomical Relations
Overall, the gastrocnemius muscle is one of the muscles of the superficial part of the posterior compartment of the leg. It is a thick, fusiform type of skeletal muscle and is composed of two heads:
- a slightly larger medial head;
- a slightly smaller lateral head.
The medial and lateral heads of gastrocnemius are two of the three muscles that form the triceps surae muscle, the other being the soleus muscle.
The gastrocnemius muscle is located:
- anterior (deep) to the tendon of the semimembranosus muscle and the biceps femoris tendon;
- posterior (superficial) to the oblique popliteal ligament, the medial and lateral subtendinous bursae of gastrocnemius, the popliteus and soleus muscles, the tendon of the plantaris muscle, the posterior tibial vessels, and the tibial nerve.
Actions & Testing
Overall, the gastrocnemius muscle is involved in multiple actions:
- plantarflexes the foot at the ankle joint;
- flexes the leg at the knee joint.
The gastrocnemius muscle cannot be tested in isolation, therefore all three muscles of the triceps surae are tested simultaneously by plantarflexing the foot at the ankle joint against resistance, during which both the gastrocnemius muscle and calcaneal tendon can be seen and palpated (Sinnatamby, 2011).
References
Sinnatamby, C. S. (2011) Last's Anatomy: Regional and Applied. ClinicalKey 2012: Churchill Livingstone/Elsevier.
