Pain down the leg (sciatica): causes, red flags and when to get it checked

The sciatic nerve is formed from nerve roots in the lower spine and runs through the buttock into the leg. When a root is squeezed or inflamed by a bulging disc, narrowing of the spinal canal or tight muscle, pain is felt along the area it supplies, often more than the back itself.

• Lumbar disc prolapse (slipped disc) irritating a nerve root, often after lifting or bending.

• Spinal stenosis: narrowing of the canal with age, causing leg pain and heaviness on walking that eases with sitting or bending forward.

• Degenerative changes and bone spurs pressing on a nerve root.

• Piriformis syndrome and deep gluteal pain, where a tight buttock muscle irritates the sciatic nerve.

• Spondylolisthesis: slipping of one vertebra over another.

• Hip joint arthritis, sacroiliac joint pain and trochanteric pain, which can mimic leg pain.

• Diabetic neuropathy and other nerve problems.

• Spinal tumour, infection or cauda equina syndrome, which are uncommon but serious.

Numbness in the saddle area, new bladder or bowel problems, weakness such as foot drop, pain in both legs, fever, history of cancer, unexplained weight loss, progressive worsening, severe pain after trauma, or constant night pain need urgent assessment.

• Call 999 or go to A&E: saddle numbness, new bladder or bowel loss, or both legs weak or numb.

• Same-day GP: leg weakness developing quickly, a dragging foot, or severe pain with fever.

• GP within days to weeks: leg pain not improving after about 2 weeks of self-care, or with weakness.

• Routine: mild sciatica that is gradually improving.

The doctor asks about pain location and character, tingling, numbness, weakness, bladder and bowel function, what worsens or eases it, red-flag features, work and activities. They test strength, reflexes, sensation, walking, heel and toe walking, and straight-leg raise.

• No tests are required for most people in the first weeks.

• MRI lumbar spine: if pain is severe and persistent, or red flags, or when considering injection or surgery.

• Nerve conduction studies: occasionally, to clarify nerve involvement.

• Blood tests and other imaging: if infection or tumour is suspected.

• Hip examination and imaging if the hip is a possible source.

Stay as active as pain permits, avoid prolonged bed rest, and use heat or cold packs. Simple painkillers may help; nerve-pain medicines are prescribed for some people. Physiotherapy exercises and walking are recommended. Avoid prolonged sitting and heavy lifting during the flare.

The NHS route is a GP and physiotherapy, with spinal pain clinics, injections or surgical review for persistent pain. Private spinal consultation, MRI and injections are available directly.