The nerve supplying the gastrocnemius is the tibial nerve, which arises from the sciatic nerve. It carries fibres from the anterior rami of the S1 and S2 spinal nerves and runs through the posterior compartment of the leg. As it travels downward, it passes deep to the soleus and gives off branches that innervate the gastrocnemius. The tibial nerve enters the popliteal fossa, where it lies medial to the common fibular nerve and superficial to the popliteal artery and vein. Within this region, it