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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 spinal 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).
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