The sciatic nerve branches as it leaves the spine and extends down both legs to the feet. Symptoms can usually be felt from the buttocks to below the knee, fanning out across the back of the thigh and to the outer calf. Sometimes the foot and toes can be affected. Normally it only affects one side of the body, so should be referred if both legs are affected.11,12

Sciatica occurs in about 5%-10% of people with non-specific low back pain and sciatica symptoms can predominate over other back pain symptoms.11

Serious conditions which share similar symptoms to sciatica include:10,11,13

·       cauda equina syndrome – a severe form of spinal stenosis following a sudden compression of the nerves in the lower spine with sciatic pain on both sides;

·       spinal fracture – this could arise from a known trauma such as a road accident or fall, but could also happen with strenuous lifting in people with osteoporosis or those using corticosteroids;

·       cancer – primary cancer of the spine is rare, but potentially 30%-70% of cancer patients may develop spinal metastases; those most likely to metastasise to the spine include breast, lung, gastrointestinal, prostate, renal, and thyroid cancer;

·       infection and inflammation – eg in the space around vertebral discs (discitis), in vertebral bones (vertebral osteomyelitis), or a spinal epidural abscess.

Non-malignant tumours can also occur along the spine which can compress the spinal cord and nerve roots causing pain.11