The sciatic nerve is formed from the L4 to S3 segments of the sacral plexus, a collection of nerve fibres that emerge from the sacralpart of the spinal cord. The fibres unite to form a single nerve in front of the piriformis muscle. The nerve passes beneath piriformis and through the greater sciatic foramen, exiting the pelvis. From here, it travels down the posterior thigh to the popliteal fossa. The nerve travels in the posterior compartment of the thigh behind superficial to the adductor magnus muscle, and is itself in front of deep to one head of the biceps femoris muscle. At the popliteal fossa, the nerve divides into its two branches:

• The tibial nerve, which travels down the posterior compartment of the leg into the foot
• The common peroneal nerve (also called the common fibular nerve), which travels down the anterior and lateral compartments of the leg into the foot

The sciatic nerve is the largest nerve in the human body.

Tibial and common peroneal nerve (aka common fibular nerve)

Function

The sciatic nerve supplies sensation to the skin of the foot, as well as the entire lower leg (except for its inner side). Sensation to skin to the sole of the foot is provided by the tibial nerve, and the lower leg and upper surface of the foot via the common fibular nerve.

The sciatic nerve also innervates muscles. In particular:

• Via the tibial nerve, the muscles in the posterior compartment of the leg and sole of the foot (plantar aspect).
• Via the common peroneal nerve (also called the common fibular nerve), the muscles in the anterior and lateral compartments of the leg.

Clinical significance

Sciatica (Known as Gridhrasi in Ayurveda: Type - vataj & vatkaphaj)