The Difference Between Bulging Disc and Herniated Disc

Before we dive into the details of a bulging disc and herniated disc is important to understand the basics of the spine and disc anatomy.

Spine Anatomy: Your spine serves the essential functions of providing your body support and structure, allowing you to stand, bend, and twist. The spine also protects your spinal cord (part of your central nervous system) which is a highway of nerve signals allowing you to move and feel sensations. The spine is comprised of 33 bones which are divided into three major sections:

  • Cervical: seven vertebrae that form the neck
  • Thoracic: twelve vertebrae that form the upper and mid-back
  • Lumbar: five vertebrae that form the lower back

Each vertebra is separated by a fibrous intervertebral disc (IVD) which is made up two parts:

  • Nucleus pulposus: This is the jelly-like inner core of the disc. It is made up of roughly 80% water as well as collagen fibers. Its elasticity allows each disc to act as a shock absorber for the spine. 
  • Annulus fibrosus: The annulus is made up of seven to 15 layers of fibers surrounding and protecting the nucleus. Each has a slight arch or curvature of about 30° that provides traction and structural support for the disc.

When your spine moves the discs in your adjust slightly to support the vertebrae. For example, when you bend over the anterior (front of your disc) compresses and the posterior (back of the disc) stretches.



Bulging Disc vs Herniated Disc

Bulging Disc

What is a bulging disc?

Unlike a herniated disc, when the nucleus breaks through the annulus, a bulging disc protrudes outward but the outer layers of the annulus remains intact. However, because the disc protrudes into the spinal canal, it can still compress a nerve root. Disc bulge is also called disc prolapse.

Herniated Disc

What is a herniated disc?

When a disc herniates, the soft nucleus spurts out through a tear in the annulus. Because there is limited space in the spinal canal, the nucleus can compress a nerve root or the spinal cord. The nucleus can extrude into the spinal canal, foramen, on either side of the disc, or in some rare cases, in multiple places called multifocal extruded discs. Typically, a disc that herniates is in the final stages of degeneration. Although herniated discs can occur in any area of the spine, they are more common in the lumbar region.

Other terms used describe herniated discs include disc extrusionslipped disc, or ruptured disc.

Free Fragments

Free Fragments

In some cases a piece or pieces of the herniated disc might break off, these are called free fragments. A free fragment, also known as a sequestered disc, can break off in the spinal canal and apply pressure on the spinal cord which can result in severe pain and injury.

Types of Herniated and Bulging Discs

Herniated and Bulging discs can occur in the Cervical, Thoracic, or Lumbar regions of the spine.

  • Cervical disc herniation: This is when a disc herniates in the neck. It is one of the most common causes of neck pain.
  • Thoracic disc herniation: This is when a disc herniates in the upper or mid-back.
  • Lumbar disc herniation: This is when a disc herniates in the lower back. It is a common cause of lower back pain.

Herniated and Bulging discs can also be classified by the area of the disc they protrude into (herniation zone).

  • Central: When the disc extrudes into in the spinal cord.
  • Subarticular(Lateral Recess or Paracentral): When the disc extrudes between the spinal cord and the foramen (the space through which the nerves exit the spinal canal).
  • Foraminal(Lateral): Disc extrusion into the foramen.
  • Extraforaminal(Far Lateral): Disc extrusion beyond the foramen.


Bulging Discs Classification

Asymmetric Disc Bulge

Asymmetric disc bulge (Broad-based disc bulge): The bulge involves 25 to 50% of the disc’s circumference.

Circumferential Disc Bulge

Circumferential disc bulge (Diffuse disc bulge): The bulge extends beyond the entire disc circumference.

Herniated Disc Symptoms

Overall, symptoms of a herniated disc include: pain throughout an arm or leg, burning or tingling sensations in the affected area, muscle weakness, pain that worsens after pronlonged sitting or standing, pain or numbness that radiates down one side of the body, pain that becomes more severe during the night or Imparied ankle or knee reflexes. Herniated disc pain may be mild to severe.

Symptoms by Region of the Spine

Herniated Cervical Disc(neck): Pain shooting down the arm to the fingertips, numbness, tingling, or weakness in the shoulder, arm or hand, difficulty walking or maintaining balance or problems gripping or handling things.

Herniated Thoracic Disc (upper and mid-back): Pain from the lower neck to the mid-back, chest pain, headaches when lying down, difficulty walking, tingling, numbness, or burning sensation in the legs, weakness in the legs or problems with the bladder or bowels.

Herniated Lumbar Disc (lower back): Pain in your lower back, buttocks, hamstring, calf, or feet, numbness or tingling in the affected leg, shooting pain down you leg, weakened leg muscles, burning or sharp pain in your leg that worsens when standing long periods of time, difficulty controlling the bladder or bowels, difficulty walking, abnormal ankle and knee reflexes, poor coordination, difficulty lifting the feet or cramping in the lower back or legs.

Causes of a Herniated Disc

The most common cause of disc herniation is age-related wear and tear. This is known as disc degeneration. As your body ages, the amount of water in your vertebral discs decreases, making them less flexible and more prone to tearing. Certain motions, such as twisting, turning, or lifting can also cause a herniated disc. Although less common, an injury such as a car accident or a blow to the back can cause a herniated disc.

Causes of a Bulging Disc

Like a herniated disc, the most common cause of a bulging disc is degenerative disc disease. A bulging disc may also be caused by neck or back strain brought on by repetitive movements, lifting heavy objects, and poor posture. This condition can also be caused by trauma such as a blow to the back, although this is rare. 

  • Wear and tear caused by degenerative disc disease
  • Strain due to heavy lifting and repetitive movements
  • Poor posture while standing or sitting
  • A hereditary condition

Herniated and Bulging Disc Risk Factors

Risk factors for these conditions include:

  • Men aged between 30 and 50 years are more likely than women to suffer a herniated disc.
  • People who have physically demanding jobs, such as those which involves repetitive motion or heavy lifting. 
  • Men and women who are obese or overweight are at risk because of the excess weight on their spine. They are also more likely to have the same disc herniate again.
  • Smoking tobacco increases the risk of a herniated disc because nicotine reduces the flow of blood to the vertebral discs. Not only does this increase disc degeneration, but it also slows down the healing process.
  • Your risk of a herniated or bulging disc is increased if one or both of your parents suffer from these conditions.