The sciatic nerve (L4-S3) consists of 2 separate nerves within a common sheath that separate at a variable location in the thigh (the peroneal division of the sciatic nerve is more vulnerable to injury than the tibial division)
In the popliteal fossa the nerve gives off branches to gastrocnemius, popliteus, soleus and plantaris muscles, an articular branch to the knee joint, and a cutaneous branch that will become the sural nerve. The sural nerve is joined by fibres from the common fibular nerve and runs down the calf to supply the lateral side of the foot.
Below the soleus muscle the nerve lies close to the tibia and supplies the tibialis posterior, the flexor digitorum longus and the flexor hallucis longus. The nerve passes into the foot running posterior to the medial malleolus. Here it is bound down by the flexor retinaculum in company with the posterior tibial artery.