What are the causes of sciatica?

Doctor's Answer

Photo of Dr Shee Yan Fong
Dr Shee Yan Fong

Orthopaedic Surgeon

What is sciatica?


Any type of pain and/or neurological symptom that originates from the sciatic nerve is referred to as sciatica. The sciatic nerve is the largest nerve in the human body. It is formed by the union of 5 nerve roots from the lower spine. It passes deep in the buttock and down the back of the thigh all the way to the heel and sole of the foot. The sciatic nerve serves a vital role in connecting the spinal cord with the skin and muscles of the thigh, leg, and foot.

Symptoms of sciatica

The symptoms of sciatica are typically felt along the path of the nerve (i.e. from your back down along your leg). You might feel: [1]

  • Mild aches
  • Burning pain
  • Numbness
  • Muscle weakness, etc.

Sciatica happens when there are issues with your sciatic nerve

The sciatic nerve may be irritated, compressed, or inflamed by a number of problems in the lower back, causing sciatica [2]. Some conditions may also cause sciatica because they cause a direct physical force to the nerve. When that happens, it is important to consult a spine specialist as soon as possible. Often times, they will send you for an MRI scan to fully diagnose the condition.

  1. Herniated discs. A disc in the lower back may bulge or herniate, causing irritation, and/or compression of a sciatic nerve root [3].
  2. Foraminal stenosis. Stenosis, or narrowing of the intervertebral opening through which the sciatic nerve roots travel, may compress or irritate the sciatic nerve. Other degenerative changes in the spine, such as thickening of facet joint capsules and/or ligaments, may also directly compress the sciatic nerve [4].
  3. Segmental instability. Instability of a vertebral segment that occurs if one vertebra slips over the one below it (spondylolisthesis), vertebral defects (spondylolysis), or complete dislocation of one or more vertebrae may directly compress the nerve root(s) of the sciatic nerve.
  4. Rarely, tumours, cysts, infection, or abscesses in the lower spine or pelvic region may also compress the sciatic nerve [5].


1. Sciatica - Symptoms and causes. Mayo Clinic. Published 2019.

2. NHS Choices. Sciatica. Published 2019. ‌

3. Koes BW, van Tulder MW, Peul WC. Diagnosis and treatment of sciatica. BMJ. 2007;334(7607):1313-1317. doi:10.1136/bmj.39223.428495.be‌

4. Foraminotomy: MedlinePlus Medical Encyclopedia. Medlineplus.gov. Published 2017. ‌

5. Gopinath P. Lumbar segmental instability: Points to ponder. Journal of Orthopaedics. 2015;12(4):165-167. doi:10.1016/j.jor.2015.09.005 ‌

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