The Truth About Sciatica

The term sciatica refers to sciatic nerve symptoms that originate in the lower spine, radiate deep into the buttock, and travel down into the leg and foot. Sciatica is so common that many use the term in an overly broad manner, incorrectly applying it to other types of lower back and leg problems.

Sciatica Is the Symptom of an Underlying Condition

The term sciatica refers to a set of symptoms caused by an underlying medical condition and it’s not an actual medical diagnosis. ¹ Cook CE, Taylor J, Wright A, Milosavljevic S, Goode A, Whitford M. Risk Factors for First Time Incidence Sciatica: A Systematic Review. Physiotherapy Research International. 2013;19(2):65-78. doi:10.1002/pri.1572. The symptoms occur when a nerve root in the lower spine is irritated or compressed by a chemical or mechanical source.

The sciatic nerve is formed by the union of 5 nerve roots (L4 to S3) in the lumbar and sacral spine. ² Giuffre BA, Jeanmonod R. Anatomy, Sciatic Nerve. [Updated 2018 Dec 16]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK482431/. Irritation or compression of any of these nerve roots (also called radiculopathy) can cause pain, numbness, and/or weakness along the entire distribution of the nerve. Nerve root irritation is most common at the L4, L5, and/or S1 level of the spine. ³ Hernández C.P., Sanchez N., Navarro-Siguero A., Saldaña M.T. (2013) What is Sciatica and Radicular Pain?. In: Laroche F., Perrot S. (eds) Managing Sciatica and Radicular Pain in Primary Care Practice. Springer Healthcare, Tarporley. https://doi.org/10.1007/978-1-907673-56-6_1.

Common causes of sciatica are described below. ⁴ Davis D, Vasudevan A. Sciatica. [Updated 2019 Feb 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK507908/.

Lumbar disc herniation

The bulging and/or extrusion of the inner core of a spinal disc in the lower back may cause nerve root irritation or compression through 2 mechanisms: the leaking of certain chemicals from the disc and direct mechanical pressure.

Lumbar degenerative disc disease

Weakened discs in the lower back allow excess motion in the spine and may cause irritation of the nerve roots. Read more about Lumbar Degenerative Disc Disease

Isthmic spondylolisthesis

A condition where one vertebra slips over another and pinches a nerve root. Read more about Isthmic Spondylolisthesis

Lumbar spinal stenosis

Narrowing of bony openings in the spine, which may cause compression of nerve roots as they exit the spinal canal. Read more about Lumbar Spinal Stenosis

Rarely, spinal tumors and infections may cause sciatica and require immediate medical attention.

Read more about Sciatica Causes

Sciatica Symptoms Vary Based on the Affected Nerve Roots

Sciatica pain travels down from the lower back, into the leg, and may sometimes affect the feet and toes. Other sensations associated with sciatica may include tingling, numbness, burning, and/or a prickly feeling.

Depending on the location of nerve compression, different sciatica symptoms may be experienced. For example, the L5 and S1 nerve roots are commonly affected and may cause the following symptoms:

• Sciatica from the L5 nerve root may cause pain along the outer part of the thigh and leg, and weakness while lifting the foot.
• Sciatica from the S1 nerve root may cause pain in the calf and foot, and numbness along the outer side of the foot and in the third, fourth, and fifth toes.

Typically sciatica symptoms affect one leg at a time. Rarely, both legs may be affected if the underlying cause compresses the left and right nerve roots together. ⁵ Ombregt L. The dural concept. In: A System of Orthopaedic Medicine. Elsevier; 2013:447-472.e4. doi:10.1016/b978-0-7020-3145-8.00033-8. The severity and duration of pain from sciatica can also vary. Most commonly, a sharp, burning, or searing pain may be felt. Sometimes, the pain may be a dull ache or a mild discomfort that comes and goes.

It is important to understand that sciatica is radiculopathy and originates from the sciatic nerve roots (L4 to S3) in the lower spine. ² Giuffre BA, Jeanmonod R. Anatomy, Sciatic Nerve. [Updated 2018 Dec 16]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK482431/. Sciatica-type symptoms may occur in other conditions, such as hip arthritis, piriformis syndrome, or sacroiliac joint dysfunction, but are not medically considered to be sciatica.