Lateral Head of Gastrocnemius

Origin

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

- lateral aspect of the lateral condyle of femur;

- inferior half of the lateral supracondylar line of femur.

Insertion

The fibers of the lateral head of gastrocnemius muscle travel inferiorly and converge with the fibers of the soleus muscle and the medial 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 lateral head of gastrocnemius muscle specifically, it is located:

- anterior (deep) to the biceps femoris tendon;

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

- medial to the common fibular nerve;

- lateral to the plantaris muscle, the medial head of gastrocnemius muscle, the small saphenous vein and the medial sural cutaneous nerve.

The lateral head of gastrocnemius muscle contributes to the formation of the popliteal fossa, where the muscle and tendon form its inferolateral 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.