Sciatica is pain in the lower extremity resulting from irritation of the sciatic nerve. The pain of sciatica is typically felt from the low back (lumbar area) to behind the thigh and radiating down below the knee. The sciatic nerve is the largest nerve in the body and begins from nerve roots in the lumbar spinal cord in the low back and extends through the buttock area to send nerve endings down the lower limb. The pain of sciatica is sometimes referred to as sciatic nerve pain. It will also lead to paralysis.