The main nerve traveling down the leg is the sciatic nerve. Pain associated with the sciatic nerve usually originates higher along the spinal cord when nerve roots become compressed or damaged from narrowing of the vertebral column or from a slipped disk. Symptoms can include tingling, numbness, or pain, which radiates to the buttocks legs and feet.

The spinal cord ends in the lumbar area and continues through the vertebral canal as spinal nerves. Because of its resemblance to a horse's tail, the collection of these nerves at the end of the spinal cord is called the cauda equina. These nerves send and receive messages to and from the lower limbs and pelvic organs.

The sciatic nerve is located in the back of the leg. It supplies the muscles of the back of the knee and lower leg. The sciatic nerve also provides sensation to the back of the thigh, part of the lower leg, and the sole of the foot. Partial damage to the nerve may demonstrate weakness of knee flexion (bending), weakness of foot movements, difficulty bending the foot inward (inversion), or bending the foot down (plantar flexion). A person's reflexes may be abnormal, with weak or absent ankle-jerk reflex. Several different tests can be performed to find the cause of sciatic nerve dysfunction.