What Is Sciatica?


Sciatica, or sciatic nerve pain, refers to pain that occurs when the sciatic nerve root in the lower back becomes compressed, irritated or inflamed. Sciatic nerve pain radiates from the lower back, into the buttocks, and down the legs. It is most commonly the result of a herniated or slipped disc, bone spurs, or spinal stenosis.

The type of sciatica is dependent upon one or both legs being affected and the duration of symptoms. Sciatica types include acute, chronic, alternating and bilateral.

What is the sciatic nerve?

The sciatic nerve is the longest and largest nerve in the body; its diameter is approximately the size of a penny. It is composed of two nerve roots from the lumbar (lower back) spine and three nerve roots from the sacrum (bottom of the spine). These five nerve roots unite and form a sciatic nerve on each side of the body.

Each sciatic nerve runs from the lower back, through the hip joint, into the buttock, and down each leg. The peroneal and tibial nerves are smaller nerves that branch off from the sciatic nerve, enabling movement and sensation in the thighs, knees, calves, ankles, feet and toes.


Pain associated with the sciatica nerve can be irritating, severe or debilitating; however, many cases resolve on their own within a few weeks. Symptoms of sciatica include the following:

  • Pain. Sciatic pain may be burning, sharp or shooting and may radiate from the lower back, through the buttocks, and down the front or back of the leg. Pain may worsen with movement, twisting, bending down, or coughing. Sciatica is also a common symptom of lumbar radiculopathy. Radiculopathy is the medical term for symptoms caused by irritation or compression of one or more spinal nerve roots.
  • Numbness or weakness. Tingling, numbness or weakness may be experienced in the lower back, legs, and feet. Muscle weakness may occur in the leg and foot, resulting in difficulty bending the knee or lifting the foot off the floor.
  • Symptoms on one side. It is rare that both legs are affected at the same time. A feeling of heaviness or pain is typically experienced on one side of the lower extremities.
  • Posture related symptoms. Changes in posture (e.g., standing, bending, twisting, lying down, sitting, etc.) may worsen or relieve pain. Pain may be constant or increase when lying down; therefore, lying on either the back or side with a pillow under or between the legs may help relieve pain.
  • Bowel or bladder dysfunction. In severe cases of sciatica, loss of bowel or bladder control may be experienced, which requires immediate medical attention.

When to see a doctor

A health care professional should be consulted if sciatica pain lasts longer than a week or becomes progressively worse. Medical care is also needed for the following:

  • Sudden and severe pain occurs in the lower back or leg, accompanied by leg muscle weakness.
  • Sciatica pain is the result of a traumatic injury, such as a traffic accident.
  • Control of the bowels or bladder is lost.


The most common causes of sciatica include, but are not limited to, the following:

  • Herniated or slipped disc. The most common cause of sciatica is a herniated or slipped disc. As a disc naturally degenerates with age, it can herniate, causing irritation or compression of the sciatic nerve.
  • Degenerative disc disease. Degenerative disc disease (DDD) is a condition of the spine, in which one or more of the discs between the vertebrae cause neck or back pain.
  • Spinal stenosis. Spinal stenosis is a narrowing of the spinal canal, which can place pressure on the nerves traveling throughout the spine.
  • Spondylolisthesis. Spondylolisthesis is a medical condition that primarily affects the lower back and can lead to nerve compression.
  • Osteoarthritis. Osteoarthritis involves the gradual breakdown of cartilage in one or more joints. The bones in the joint eventually rub together and can pinch the sciatic nerve.
  • Bone spurs. Bone spurs are often the result of the progression of osteoarthritis. As the overgrowth of bones form, jagged edges can place pressure on sciatic nerve roots.
  • Piriformis syndrome. The sciatic nerve is located deep inside the buttock area and runs alongside the piriformis muscle. This muscle can become irritated or spasm, which causes pressure on the sciatic nerve.
  • Vertebral fracture. A vertebral fracture is a fracture in any of the 33 vertebrae that make up the spinal column and may result in the sciatic nerve becoming compressed.
  • Cauda equina syndrome. Although rare, cauda equina is a serious condition affecting the nerve bundle at the end of the spinal cord.
  • Tumors. A tumor located in the lumbar spinal canal can compress the sciatic nerve.
  • Injury. Any type of injury to the lumbar spine or the sciatic nerve can result in sciatica.

Risk factors

Risk factors for sciatica include the following:

  • Aging
  • Obesity
  • Physical occupation—A job that requires heavy lifting, twisting, or driving for long periods increases lower back problems.
  • Prolonged sitting
  • Sedentary lifestyle
  • Diabetes
  • Osteoarthritis
  • Tobacco use
  • Injury, or previous injury, to the spine or lower back
  • Low core strength
  • Improper posture lifting weights
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