Sciatic Nerve and Sciatica

The sciatic nerve is the longest and largest nerve in the body measuring three-quarters of an inch in diameter. The sciatic nerve originates in the sacral plexus; a network of nerves in the low back (lumbosacral spine). The lumbosacral spine refers to the lumbar spine and the sacrum combined. The sciatic nerve and its nerve branches enable movement and feeling (motor and sensory functions) in the thigh, knee, calf, ankle, foot and toes. The sciatic nerve and the lumbosacral spine is pictured below.

Sciatic Symptoms
If the sciatic nerve is injured or becomes inflamed, it causes symptoms called sciatica. Sciatica can cause intense pain along any part of the sciatica nerve pathway - from the buttocks to the toes. If the nerve is compressed, caused by conditions such as a bulging or herniated disc or tumor (rare), symptoms may include a loss of reflexes, weakness and numbness besides severe pain. Sciatic nerve pain can make everyday activities such as walking, sitting and standing difficult.

How Sciatica Pain Can Spread
The sciatic nerve exits the sacrum (pelvic area) through a nerve passageway called the sciatic foramen. At the upper part of the sciatic nerve, two branches form; the articular and muscular branches. The articular branch supplies the hip joint. The muscular branch serves the leg flexor muscles; muscles that enable movement.

The sciatic nerve also enables movement (motor function) and feeling (sensory function) to the thigh, knee, calf, ankle, foot and toes. Other complex nerve structures are involved; the peroneal nerves and tibial nerves. The peroneal nerves originate from the nerve roots at the fourth and fifth lumbar spine (L4-5) and first and second levels of the sacrum (S1-2). After the peroneal nerves leave the pelvis, they travel down the front and side of the leg, and along the outer side of the knee, to the foot. The tibial nerves originate from the nerve roots at L4-5 and S1-3. The tibial nerves pass in front of the knee and downward into the foot (heel, sole, toes).