Sciatica (sometimes known as lumbar radiculopathy or low back pain with radiculopathy) features unilateral leg pain that radiates to the foot or toes and possible signs of nerve root compression, such as numbness, paraesthesia and muscle weakness. The commonest reason for sciatica, accounting for around 90 per cent of cases, is a herniated (or slipped) disc, most commonly at L4-L5 or L5-S1. Spinal stenosis (narrowing of the spinal canal), infection and cancer are other causes. Two simple tests that can aid diagnosis are raising the affected leg while it is straight (pain and nerve compression symptoms will increase below the knee) and stimulating the lateral part of the sole of the foot (the toes will splay).

Many people experience recurrent episodes of sciatica, which may last longer and cause greater disability, and certainly true remission of low back pain – a single episode that resolves and never occurs again – is rare.

Some population groups are more likely to experience non-specific low back pain, namely those who are physically inactive, or who have depression or another mental health condition. Anyone whose work involves heavy lifting or similar activities is also at increased risk. Obesity, smoking, genetic and environmental factors also play a part.