What Is Sciatica? Understanding Causes, Stages & Diagnosis

Sciatica is a common condition that affects thousands of people each year, yet many do not know what causes it, how serious it can be, or the best way to diagnose it. This guide explains what sciatica is, the cause of sciatic nerve pain, the different types of sciatica, how common it is, and the four stages of sciatica.

If you’re experiencing persistent symptoms, an early and accurate diagnosis is key. At Vitalscan, we provide rapid access to MRI scans to help determine the cause of sciatic nerve pain and support you on the path to recovery.

Sciatica describes pain that travels along the path of the sciatic nerve, which runs from the lower back through the hips, buttocks and down each leg. It is a symptom, not a condition in itself, and is usually caused by irritation, pinching or compression of the sciatic nerve.

Typical symptoms of sciatica include:

Some people experience mild discomfort, while others find that sciatica significantly interferes with daily life.

The most common cause of sciatic nerve pain is a herniated or slipped disc, which places pressure on the nerve root. However, other spinal and muscular problems can also trigger sciatica.

Because many issues can lead to sciatic nerve irritation, MRI scanning is often the most accurate way to identify the cause.

Sciatica can be categorised in different ways depending on severity and cause.

Short term, often lasting days to weeks. Usually improves with rest, pain management and physiotherapy.

Lasts longer than three months and may require further investigation or specialist care.

Pain that affects both legs but not at the same time sometimes caused by sacroiliac joint problems.

Pain affects both legs simultaneously. This is less common and can be associated with more serious spinal conditions.

Sciatica is very common, affecting around 10–40% of people at some point in their lives.

It is more frequent in adults aged 30–50 and is often linked to lifestyle factors such as:

Because symptoms can mimic other spinal conditions, a professional assessment is crucial.

While severity varies, sciatica can generally be described as progressing through four stages:

Pain begins in the lower back and may radiate to the buttocks or down the leg. Symptoms can be sharp, burning or shooting.

If untreated, sciatica may persist beyond 3 months, affecting mobility and quality of life.

Numbness, tingling and muscle weakness can develop as nerve compression increases.

Severe cases may include bowel or bladder dysfunction, significant weakness or numbness around the buttocks or anus.

This stage requires urgent medical attention.

Seek emergency care if you experience:

These may indicate a serious condition such as cauda equina syndrome, requiring urgent treatment.

Your GP or specialist will usually begin with a physical assessment. However, because symptoms can overlap with other spinal or muscular issues, a scan is often needed.

The best way to diagnose the causes of sciatica

The most accurate diagnostic test is an MRI scan of the lumbar spine, which shows:

At Vitalscan, you can book a lumbar spine MRI directly, or your GP, specialist or allied health professional can refer you.

Treatment will depend on the underlying cause but may include:

Early diagnosis helps ensure you receive the most effective treatment plan.

At Vitalscan, we provide quick and convenient access to high quality MRI scanning services, helping you understand the cause of your sciatica sooner.

Whether you’re experiencing acute sciatica or chronic nerve pain, a lumbar spine MRI can help guide treatment and improve outcomes.