Sciatica is a condition involving impaired movement and/or
sensation in the leg, caused by damage to the sciatic nerve. This nerve runs from
the lower part of the spinal cord, down the back of the leg, to the foot. Injury to or
pressure on the sciatic nerve can cause the characteristic pain of sciatica: a sharp or
burning pain that radiates from the lower back or hip, possibly following the path of the
sciatic nerve to the foot.
Information about Sciatica
Sciatica is a form of peripheral neuropathy. It occurs when
there is damage to the sciatic nerve, located in the back of the leg. This nerve controls
the muscles of the back of the knee and lower leg and provides sensation to the back of
the thigh, part of the lower leg and the sole of the foot. Incomplete damage to the
sciatic nerve may appear identical to damage to one of the branches of the sciatic nerve
(tibial nerve dysfunction or common peroneal nerve dysfunction).
A problem in a single nerve group, such as the sciatic nerve, is classified as a mononeuropathy. The usual causes are direct trauma (often
due to an injection into the buttocks), prolonged external pressure on the nerve, and
pressure on the nerve from nearby body structures. It can also be caused by entrapment --
pressure on the nerve where it passes through a narrow structure. The damage slows or
prevents conduction of impulses through the nerve.
The sciatic nerve is commonly injured by fractures of the pelvis, gunshot wounds, or
other trauma to the buttocks or thigh. Prolonged sitting or lying with pressure on the
buttocks may also injure it. Systemic diseases, such as diabetes, can typically damage
many different nerves, including the sciatic nerve. The sciatic nerve may also be harmed
by pressure from masses such as a tumor or abscess, or by bleeding in the pelvis.
In many cases, no cause can be identified.
More information about Sciatica
Note: A ruptured lumbar disk in the spine may cause symptoms that simulate the symptoms
of sciatic nerve dysfunction.
The sciatic nerve is the largest and longest nerve in the body. About the thickness of
a person's thumb, it spans from the lower back to the foot. The nerve originates in the
lower part of the spinal cord, the so-called lumbar region. As it branches off from the
spinal cord, it passes between the bony vertebrae (the component bones of the spine) and
runs through the pelvic girdle, or hip bones. The nerve passes through the hip joint and
continues down the back of the leg to the foot.
Sciatica is a fairly common disorder and approximately 40% of the population
experiences it at some point in their lives. However, only about 1% have coexisting
sensory or motor deficits. Sciatic pain has several root causes and treatment may hinge
upon the underlying problem.
Of the identifiable causes of sciatic pain, lumbosacral radiculopathy and back strain
are the most frequently suspected. The term lumbosacral refers to the lower part of the
spine, and radiculopathy describes a problem with the spinal nerve roots that pass between
the vertebrae and give rise to the sciatic nerve. This area between the vertebrae is
cushioned with a disk of shock- absorbing tissue. If this disk shifts or is damaged
through injury or disease, the spinal nerve root may be compressed by the shifted tissue
or the vertebrae.
This compression of the nerve roots sends a pain signal to the brain. Although the
actual injury is to the nerve roots, the pain may be perceived as coming from anywhere
along the sciatic nerve.
The sciatic nerve can be compressed in other ways. Back strain may cause muscle spasms
in the lower back, placing pressure on the sciatic nerve. In rare cases, infection,
cancer, bone inflammation, or other diseases may be causing the pressure. More likely, but
often overlooked, is the piriformis syndrome. As the sciatic nerve passes through the hip
joint, it shares the space with several muscles. One of these muscles, the piriformis
muscle, is closely associated with the sciatic nerve. In some people, the nerve actually
runs through the muscle. If this muscle is injured or has a spasm, it places pressure on
the sciatic nerve, in effect, compressing it.
In many sciatica cases, the specific cause is never identified. About half of affected
individuals recover from an episode within a month. Some cases can linger a few weeks
longer and may require aggressive treatment. In some cases, the pain may return or
potentially become chronic.