What Are The Causes Of Sciatica?

By Dr. Eleanor Smith, DPT
Medically Reviewed by Dr. Alex Roberts, BSc Physiology
Last Updated: January 2026

Sciatica isn’t random.

It doesn’t appear “out of nowhere”.

Sciatica happens when the sciatic nerve becomes irritated, compressed, or inflamed.

The pain is a reaction, not the root problem itself.

Understanding what causes sciatica makes it much easier to stop it coming back.

The Most Common Causes Of Sciatica

The most common causes of sciatica include:

• Bulging or herniated disc in the lower back
  
  

• Muscle tightness or spasm compressing the nerve
  
  

• Spinal wear and tear reducing nerve space
  
  

These are the primary sciatica root causes seen in long-term cases.

Can Poor Posture Cause Sciatica?

Yes. Poor posture can contribute to sciatica.

• Slouching in chairs
  
  

• Leaning to one side when sitting
  
  

• Standing with uneven weight distribution
  
  

Over time, this increases pressure around the nerve and fuels inflammation.

Can Sitting Cause Sciatica?

Prolonged sitting is a very common trigger.

Sitting can cause sciatica because it:

• Increases pressure on the lower spine
  
  

• Tightens hip and glute muscles
  
  

• Reduces blood flow around the nerve
  
  

This is why desk work and long drives often make symptoms worse.

Can Walking Wrong Cause Sciatica?

Yes. Walking mechanics matter.

Poor walking patterns can:

• Stress one side of the lower back
  
  

• Overload the hip and glute muscles
  
  

• Create muscle imbalances around the nerve
  
  

Over time, this contributes to ongoing irritation.

Other Common Underlying Causes Of Sciatica

Sciatica can also develop from:

• Heavy lifting with poor technique
  
  

• Pregnancy-related pelvic changes
  
  

• Direct injury or trauma
  
  

• Muscle imbalances in the hips or core
  
  

These don’t always cause immediate pain, but they often trigger inflammation that builds over time.

Not sure if this is sciatica yet?

See the full list of sciatica symptoms and how to confirm it.

The Real Underlying Cause Of Sciatica

In many cases, the initial trigger improves.

But:

• Inflammation remains active
  
  

• Nerve sensitivity stays high
  
  

• Pain keeps returning
  
  

This is why sciatica often becomes persistent.

If you feel like you may have sciatica, find out the best fixes for sciatica in 2026 that actually works. Click Below.

Best Fixes For Sciatica