Medial Head of Gastrocnemius

Origin

The medial head of gastrocnemius muscle originates, via a short, flat tendon, from the:

- posterior aspect of the medial condyle of femur;

- lateral aspect of the popliteal surface of femur.

Insertion

The fibers of the medial head of gastrocnemius muscle travel inferiorly and converge with the fibers of the soleus muscle and the lateral head of gastrocnemius 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 a slightly larger medial head and 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.

With regard to the medial head of gastrocnemius muscle specifically, it is located:

- anterior (deep) to the tendon of the semimembranosus muscle;

- posterior (superficial) to the oblique popliteal ligament, the medial subtendinous bursa of gastrocnemius, the popliteus and soleus muscles, the tendon of the plantaris muscle, the posterior tibial vessels, and the tibial nerve;

- medial to the plantaris muscle, the lateral head of gastrocnemius muscle and the small saphenous vein;

- lateral to the great saphenous vein and the saphenous nerve.

The medial head of gastrocnemius muscle contributes to the formation of the popliteal fossa, where the muscle and tendon form its inferomedial boundary.

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.