Sciatica: What Is Actually Causing Your Leg Pain?

If you've developed pain travelling from your lower back into your leg, you've probably heard the word “sciatica.”

It's a term most people recognise, and it's commonly used to describe back-related leg pain.

But there's an important problem with the term:

Sciatica doesn't really tell us what's causing your symptoms.

In clinical practice, we don't use “sciatica” as a particularly specific diagnosis. Several different mechanisms can cause pain, tingling, numbness or other symptoms in the leg when someone has a problem involving the lower back.

Some involve the nerves.

Some don't.

And they can require very different approaches to treatment.

So while we'll use the word sciatica here because it's the term most people search for, the more useful question is:

“What's actually causing my leg pain?”

Not All Back-Related Leg Pain Is Nerve Pain

When someone has pain travelling from their lower back into their leg, there are several possible explanations.

The four broad mechanisms we commonly consider are:

Nerve root compression Peripheral nerve sensitivity Increased nervous system sensitivity Referred pain

These can also coexist, which is one reason these presentations can sometimes be difficult to assess.

Let's look at them in simple terms.

1. Nerve Root Compression

This is probably what most people imagine when they hear “sciatica”.

Something within the spine, often a disc, can irritate or compress one of the nerve roots that contributes to the sciatic nerve.

This can produce symptoms such as:

• Pain travelling into the leg • Numbness • Tingling • Weakness • Changes in reflexes

Importantly, nerve compression doesn't necessarily cause pain.

Depending on the severity and location of the compression, someone may experience predominantly numbness or weakness.

Treatment can involve modifying activities, specific exercise and other physiotherapy interventions.

However, if numbness or weakness is progressively worsening, medical assessment is important and, in some cases, surgical intervention may be required.

2. A Sensitive Peripheral Nerve

A nerve can also become sensitive without being significantly compressed.

In this situation, the nerve may be more sensitive to movement, stretch or mechanical loading.

People may describe:

• Pins and needles • Tingling • Burning • Electric or unusual sensations

Treatment is generally focused on reducing whatever is irritating the nerve and gradually restoring its tolerance to movement and load.

Specific exercises may sometimes be used to help restore normal nerve movement and sensitivity.

3. A More Sensitive Nervous System

Sometimes the nervous system itself becomes increasingly sensitive.

The brain and nervous system are constantly assessing information from the body and deciding how much protection is required. In some persistent pain conditions, this system can become overly protective and respond strongly to relatively normal inputs.

Symptoms can be more widespread or unusual and may include:

• Burning • Itching • Crawling sensations • Changes in sensitivity

These symptoms may not follow the pathway of one particular nerve or stay within a specific area.

Treatment in these cases is generally less about trying to physically “fix” a structure and more about education and gradually exposing the person to movement and load.

Depending on the individual, psychological support and medication may also form part of a broader treatment approach.

4. Referred Pain

This is one of the most important things to understand.

The lower back can produce pain that is felt in the leg without the sciatic nerve being the source of the problem.

This is known as referred pain.

The nervous system doesn't always provide us with a perfectly accurate map of where a pain signal originates. As a result, something happening in the lower back can sometimes be perceived as pain further down the leg.

In these situations, treatments aimed specifically at the sciatic nerve may not be particularly useful.

Instead, treatment is directed towards the back and the factors contributing to the problem.

This might include specific exercise, appropriate manual therapy and modifying other activities or loads that may be contributing to the symptoms.

These Problems Can Overlap

The four categories above aren't completely separate.

Someone can have some degree of nerve compression alongside nerve sensitivity or referred pain.

This is one reason why simply looking at where the pain is isn't enough to determine what's happening.

A good assessment needs to consider the whole presentation.

What About an MRI?

This is where things can become confusing.

An MRI can be very useful when there is a clinical reason to investigate the spine.

But an MRI doesn't automatically tell us what is causing your pain.

Disc bulges, disc degeneration and other changes are common in people who have no back or leg pain at all.

So an MRI might show something that looks like it could explain your symptoms, but that finding doesn't necessarily mean it is the source of your pain.

This is why imaging needs to be interpreted alongside a detailed clinical assessment.

So, Do You Actually Have Sciatica?

It's actually a less useful question than it sounds.

“Sciatica” is a familiar term for back-related leg pain, but it isn't specific enough to tell us what is happening.

Two people can both describe their symptoms as “sciatica” while having completely different underlying mechanisms.

And if the underlying problem is different, the appropriate treatment may be different too.

The goal of an assessment isn't simply to give your pain a name.

It's to understand:

What is most likely contributing to your symptoms?

What can you safely continue doing?

What needs to be modified?

What treatment is most appropriate?

If you're experiencing back or leg pain in Tokyo, particularly if you're developing numbness, weakness or worsening symptoms, an assessment with an experienced physiotherapist can help determine what may be contributing to your symptoms.

At Club 360 Tokyo, our physiotherapists can assess your symptoms and help develop an appropriate treatment and rehabilitation plan.

Not all leg pain is sciatica. Understanding the cause matters.