Sciatica

Sciatica is a term used to describe the symptoms of pain, tingling, numbness, or weakness in the leg that is caused by irritation and/or compression of the sciatic nerve. Sciatica originates in the lower back, radiates deep into the buttock, and travels down the leg.

Sciatica (sometimes known as radiculopathy) is a description of symptoms, not a diagnosis. A herniated disc, spinal stenosis, degenerative disc disease and spondylolisthesis can all cause sciatica.

What Does Sciatica Feel Like?

The symptoms of sciatica are commonly felt along the path of the large sciatic nerve. Sciatica is often characterized by one or more of the following features:

• Pain. Sciatica pain is typically felt like a constant burning sensation or a shooting pain starting in the lower back or buttock and radiating down the front or back of the thigh and leg and/or feet.

• Numbness. Sciatica pain may be accompanied by numbness in the back of the leg. Sometimes, tingling and/or weakness may also be present.

• One-sided symptoms. Sciatica typically affects one leg. The condition often results in a feeling of heaviness in the affected leg. Rarely, both legs may be affected together.

• Posture induced symptoms. Sciatica symptoms may feel worse while sitting, trying to stand up, bending the spine forward, twisting the spine, lying down, and/or while coughing. The symptoms may be relieved by walking or applying a heat pack over the rear pelvic region.

It is important to note that any type of lower back pain or radiating leg pain is not sciatica. Sciatica is specific to pain that originates from the sciatic nerve.

Sciatica Is the Symptom of an Underlying Medical Condition

Sciatica is a term used to describe a set of symptoms caused by an underlying medical condition; it is not a medical diagnosis.

Common medical conditions that may cause sciatica include1:

• A herniated lumbar disc

• Lumbar spinal stenosis

• Lumbar degenerative disc disease, general degenerative changes in vertebrae or discs

• Spondylolisthesis

• Muscle spasm and/or inflammation of the lumbar and/or pelvic muscles

• Sacroiliac joint dysfunction

Rarely, tumors, blood clots, or other conditions in the lower spine may cause sciatica.

In addition to the terms that identify the underlying pathologies that cause sciatica, the terms lumbar radiculopathy or radicular pain may be used interchangeably with the term sciatica.

The Course of Sciatica

Often, a particular event or injury does not cause sciatica—rather it tends to develop over time. Sciatica affects 10% to 40% of the population, typically around the age of 40 years. Sciatica is found to be common in certain types of occupation where physically strenuous positions are used, such as machine operators or truck drivers. Specifically, people who often bend their spine forward or sideways or raise their arms frequently above the shoulder level may be at risk of sciatica.

The vast majority of people who experience sciatica typically get better within 4 to 6 weeks with nonsurgical sciatica treatments. If severe neurological deficits are present, recovery may take longer. An estimated 33% of people, however, may have persistent symptoms and may have severe nerve compression with progressive symptoms in which surgery may be indicated.

When Sciatica Is Serious

Certain symptoms of sciatica may indicate a serious medical condition, such as cauda equina syndrome, infection, or spinal tumors. These symptoms may include, but are not limited to:

• Progressive neurological symptoms, such as leg weakness

• Symptoms in both legs

• Bowel and/or bladder dysfunction

• Sexual dysfunction

It is advised to seek medical attention immediately if such symptoms develop. Sciatica that occurs after an accident or trauma, or if it develops in tandem with other symptoms like fever or loss of appetite, is also cause for prompt medical evaluation.

Sciatica Symptoms

The symptoms of sciatica may range from infrequent and irritating to severe and debilitating. The symptoms depend on the specific spinal nerve root that is irritated and/or compressed at the origin of the sciatic nerve. One or more nerve roots may be affected together. 

While some symptoms are specific to nerve roots, other symptoms are common and occur in all sciatica types.

Common Sciatica Symptoms

Usually, sciatica affects only one leg at a time and the symptoms radiate from the lower back or buttock to the thigh and down the leg. Sciatica may cause pain in the front, back, and/or sides of the thigh and leg. A few common symptoms seen in sciatica are:

• Pain. Sciatica pain may be constant or intermittent. The pain is usually described as a burning sensation or a sharp, shooting pain. The pain is usually more severe in the leg compared to the back. Leg pain commonly occurs more in the calf region below the knee compared to other parts of the leg.

• Altered sensation. Numbness, tingling, and/or a pins-and-needles sensation may be felt at the back of the leg.

• Weakness. Weakness may be felt in the leg and foot. A feeling of heaviness in the affected leg may make it difficult to lift the foot off the floor.

• Change in posture may aggravate or relieve pain. Certain postures may affect sciatica pain:

• Sciatica pain may feel worse while sitting, trying to stand up, standing for a long time, bending the spine forward, twisting the spine, and/or while coughing.

• Pain may increase or remain constant while lying down, causing disturbed sleep. Lying on the back with the knees slightly elevated and propped up with a pillow, or lying on the side with a pillow between the legs, may help relieve the pain in such cases.

• The pain may be relieved while walking, applying a heat pack to the rear pelvic area, or doing pelvic exercises.

Types of Sciatica

Depending on the duration of symptoms and if one or both legs are affected, sciatica can be of different types:

• Acute sciatica. Acute sciatica is a recent onset, 4 to 8-week duration of sciatic nerve pain.

• Chronic sciatica. Chronic sciatica is persistent sciatic nerve pain that lasts for more than 8 weeks and usually does not subside with self-management. Depending on the cause, chronic sciatica may require nonsurgical or surgical treatment.

• Alternating sciatica. Alternating sciatica is sciatic nerve pain that affects both legs alternately. This type of sciatica is rare and may result from degenerative problems in the sacroiliac joint.

• Bilateral sciatica. Bilateral sciatica occurs in both legs together. This type of sciatica is rare and may occur due to degenerative changes in the vertebrae and/or the disc at several spinal levels, or from serious conditions such as cauda equina syndrome.

Informally, the term wallet sciatica may be used to describe sciatic pain that occurs while sitting on a wallet (or any object in the back pocket of a trouser).

The treatment of sciatica is focused on addressing the cause of symptoms. It’s important to consult with a doctor for a correct diagnosis, to check for the possibility of a serious medical problem, and for effective treatment.

Sciatica Causes

Sciatica is the symptom of an underlying medical condition. Understanding the possible causes of sciatica can help focus treatment on addressing the root problem rather than just masking the symptoms.

The mechanism of sciatic nerve injury is either a result of direct nerve compression, inflammation, an abnormal immune system response of the body, or a combination of all these factors.

Common Causes of Sciatica

• Lumbar herniated disc. Research suggests that up to 90% of sciatica is caused by a lumbar herniated disc. The herniated disc typically compresses one or more spinal nerve roots (L4 - S3) that form the sciatic nerve. A lumbar herniated disc can cause sciatica in two ways:

• Direct compression. Direct compression of the sciatic nerve can occur when a lumbar disc bulges (contained-disc-disorder) or when the soft inner material of the disc leaks out or herniates through the fibrous outer core (non-contained disc disorder) and presses against the nerve.

• Chemical inflammation. An acidic chemical irritant from the disc material (hyaluronan) may leak out and cause inflammation and irritation in the area around the sciatic nerve.

A herniated disc may compress the sciatic nerve on one side, causing symptoms in one leg, or the disc may bulge or herniate from both sides, causing symptoms in both legs (bilateral sciatica). Bilateral sciatica may also be caused by two adjacent segments discs herniating on either side, although this possibility is rare.

• Degeneration. Degeneration of tissues in the lumbar spine can compress or irritate the sciatic nerve. Degeneration of the facet joints can also cause the synovial tissue in the joint’s capsule to inflame and increase in bulk. Degeneration of vertebral bone may cause abnormal bone growths (bone spurs or osteophytes). These abnormally bulky tissues in the lumbar spine may cause compression of one or more nerve roots of the sciatic nerve. Degenerated intervertebral discs may secrete inflammatory proteins, causing inflammation of the sciatic nerve.

• Lumbar spinal stenosis. Spinal stenosis is the narrowing of the spinal canal and is relatively common in adults older than age 60. Research suggests that lateral recess stenosis may be common in causing sciatica in the elderly population.

• Spondylolisthesis. Spondylolisthesis occurs when a small stress fracture causes one vertebral body to slip forward on another. For example, the L5 vertebra may slip forward over the S1 vertebra. Sciatica may result from nerve compression following the disc space collapse, fracture, and forward slipping of the vertebral body. Spondylolisthesis may cause bilateral sciatica and is more common in younger adults.

These conditions may develop over time or spontaneously due to trauma or physical stress injury. Motor vehicle accidents, sports injuries, or falls may cause direct injury to the sciatic nerve. Conditions such as spondylolisthesis and herniated discs may develop from physical stress injuries, such as from weightlifting.

Causes of Sciatica-Like Symptoms

Some conditions may cause typical sciatica symptoms. A few examples include:

• Piriformis syndrome. Piriformis syndrome is caused by spasms of the piriformis muscle. Sciatica symptoms may occur when the spasmodic muscle irritates or compresses the sciatic nerve at its origin. This condition is more common when the sciatic nerve is split, which is a normal variant near the piriformis muscle, or in normal anatomical variations of the piriformis muscles itself. Piriformis syndrome is also common in overuse injuries, particularly in runners and athletes.

• Sacroiliac joint dysfunction. Irritation of the sacroiliac joint—located at the bottom of the spine—can also irritate the L5 nerve, which lies on top of the sacroiliac joint, causing sciatica-type pain.

In these cases, there is no true radiculopathy or radiating nerve pain. However, the resulting leg pain typically feels like sciatica.

Less Common Causes of Sciatica

Rarely, sciatica may develop due to tumors, infection, formation of scar tissue, collection of fluid, Pott’s disease (spinal tuberculosis), or fracture in the lumbar spine. While rare, sciatica may also develop as a complication of incorrect muscular injection methods in the buttock or following a hip joint replacement surgery. Approximately 1% of