Sciatica is caused by irritation, compression, or sensitization of the sciatic nerve, most often from spinal conditions like disc herniation, stenosis, or degeneration—but not always. Muscle compression, joint dysfunction, and long-standing nerve hypersensitivity can also trigger sciatic pain. Identifying the true source of nerve irritation is essential for lasting relief. At MAPS Centers for Pain Control, diagnosis and treatment focus on the underlying trigger—not just where the pain travels.

Sciatica Isn’t a Condition—It’s a Signal

One of the most common misconceptions about sciatica is that it’s a single diagnosis.

It’s not.

Sciatica describes a pattern of nerve pain, not the reason it exists. The sciatic nerve is reacting to something—often upstream in the spine, sometimes outside it.

If you haven’t already, start with the pillar guide:
Sciatica Pain Relief in Chicago: Causes, Symptoms, and Non-Surgical Treatment Options

The Sciatic Nerve: Why So Many Problems Can Affect It

The sciatic nerve:

Originates from multiple nerve roots in the lower spine
Travels through the pelvis and buttock
Runs down the back of the leg to the foot

Because it spans such a long path, compression or irritation anywhere along the route can produce sciatica-like symptoms.

That’s why two people with “sciatica” may have very different causes—and require very different treatments.

The Most Common Causes of Sciatica

1. Herniated or Bulging Lumbar Discs

This is the most well-known cause—and for good reason.

When a disc bulges or herniates:

It can press directly on a nerve root
Chemical inflammation may irritate the nerve
Pain often worsens with sitting or bending

This type of sciatica often produces:

Sharp, shooting leg pain
Tingling or numbness
Pain that follows a specific nerve path

Related read:
How Sciatica Is Diagnosed: Imaging, Exams, and What to Expect

2. Spinal Stenosis

Spinal stenosis refers to narrowing of the spinal canal or nerve openings, most commonly from age-related degeneration.

Sciatica from stenosis often:

Worsens with standing or walking
Improves with sitting or bending forward
Affects older adults more frequently

Unlike disc herniations, stenosis-related sciatica tends to develop gradually, not suddenly.

3. Degenerative Disc Disease

As discs lose height and hydration over time, they may:

Alter spinal alignment
Increase pressure on nerve roots
Trigger chronic nerve irritation

Degenerative changes don’t always look dramatic on imaging—but they can still cause significant nerve pain.

Related read:
Chronic Sciatica: Why Pain Persists and How Long-Term Relief Is Possible

4. Facet Joint or SI Joint Dysfunction

Not all sciatica starts with a disc.

Inflammation or dysfunction in:

Facet joints (small stabilizing joints in the spine)
Sacroiliac (SI) joints

…can refer pain into the sciatic nerve distribution, mimicking classic sciatica.

This is why imaging alone doesn’t always give the full picture—diagnostic injections are often needed.

5. Muscle-Related Sciatic Nerve Compression

In some cases, the sciatic nerve is compressed outside the spine.

The most well-known example is piriformis-related compression, where a deep hip muscle irritates the nerve as it passes through the buttock.

This type of sciatica may:

Worsen with sitting
Improve with standing or walking
Not show up clearly on MRI

6. Post-Surgical or Scar-Related Nerve Irritation

After spine or hip surgery, scar tissue may:

Tether nerve roots
Alter nerve mobility
Lead to persistent sciatic pain

Even when surgery is technically successful, nerve irritation can linger.

7. Chronic Nerve Sensitization

Sometimes the original cause of sciatica has resolved—but the pain hasn’t.

In these cases, the nervous system itself becomes overactive.

This can happen when:

Nerve inflammation lasts too long
Pain signals repeat without relief
The brain and spinal cord “learn” the pain

At this stage, treating inflammation alone is often ineffective.

Related read:
Non-Surgical Sciatica Treatment Options in Chicago

Why Identifying the Cause Matters So Much

Treating sciatica without identifying the cause often leads to:

Temporary relief
Repeated flare-ups
Frustration and chronic pain

At MAPS Centers for Pain Control, diagnosis focuses on function, nerve behavior, and response to treatment, not just imaging findings.

As pain specialists often explain, “The nerve tells the truth—if you know how to listen to it.”

How MAPS Determines What’s Triggering Sciatica

A comprehensive evaluation may include:

1. Detailed history

How pain started
What worsens or improves it
Prior injuries or surgeries

2. Physical and neurological exam

Reflexes
Strength
Sensory changes

3. Imaging (when appropriate)

MRI for discs and nerve roots
X-rays for alignment and degeneration

4. Diagnostic injections

Used to confirm pain generators
Help guide treatment direction

Learn more:
How Sciatica Is Diagnosed: Imaging, Exams, and What to Expect

Sciatica vs. Other Causes of Leg Pain

Because sciatica is often assumed, it’s important to rule out other causes.

Sciatica typically includes:

Burning, electric, or shooting pain
Numbness or tingling
One-sided leg symptoms

Other leg pain may stem from:

Hip arthritis
Knee pathology
Vascular conditions
Muscle strain

Related read:
Sciatica vs Other Causes of Leg Pain: How to Tell the Difference

FAQs

Can sciatica have more than one cause?

Yes. Many patients have multiple contributing factors, such as disc degeneration combined with joint inflammation or nerve sensitization.

Does sciatica always show on MRI?

No. Muscle compression, joint dysfunction, and nerve sensitization may not appear clearly on imaging.

Why does my sciatica keep coming back?

Recurring sciatica often means the underlying trigger was never fully addressed—or nerve sensitization developed.

Is sciatica always caused by the spine?

Not always. While most cases originate in the spine, some occur outside it along the nerve’s path.

How is the cause of sciatica treated?

Treatment depends entirely on the trigger and may include injections, physical therapy guidance, neuromodulation, or a combination approach.

The Bottom Line

Sciatica is not a one-size-fits-all condition. It’s a signal that the sciatic nerve is under stress, and that stress can come from many different sources—structural, inflammatory, or neurological.

Lasting relief begins with understanding why the nerve is irritated.

At MAPS Centers for Pain Control, identifying that cause is the foundation of every personalized sciatica treatment plan.

Explore the Full Sciatica Series

Sciatica Pain Relief in Chicago: Causes, Symptoms, and Non-Surgical Treatment Options
Sciatica Symptoms Explained: When Leg Pain Is More Than Just Back Pain
How Sciatica Is Diagnosed: Imaging, Exams, and What to Expect
Non-Surgical Sciatica Treatment Options in Chicago
Chronic Sciatica: Why Pain Persists and How Long-Term Relief Is Possible
Sciatica vs Other Causes of Leg Pain: How to Tell the Difference
When to See a Sciatica Specialist in Chicago
How Long Does Sciatica Last? Recovery Timelines and Treatment Factors