The sciatica nerve is a large nerve that begins in the lower back, runs through the buttocks and extends down to the foot. Your sciatica nerve is the largest and widest single nerve in your body. Your sciatica nerve is derived from the L4 to the S3.
The sciatica nerve is formed at the sacral plexus. The sacral plexus is a group of nerve fibers that emerge from the sacral area of the spinal cord. These fibers group together to form one single nerve that runs down the back of the leg. The sciatica nerve then passes to the biceps and eventually separates into two nerve branches.
Sciatica can cause pain in the lower back, hips, buttocks, back legs and to the feet. Sciatica is usually caused by an irritation or compression of the sciatica nerve. Sciatica is commonly caused by injury but can also be caused by disease.