What is a Bulging Disc?

Have you just been told by your doctor that you have a bulging disc in your lower back or neck? Does the doctor think that the bulging disc is causing your back pain or neck pain?

Well first thing is don’t worry. There are many people out there just like you who have a bulging disc in their backs and have managed to get through a back pain episode without needing surgery. I want to show you today what is a bulging disc by explaining, in simple language, the spinal anatomy to you.

Definition of a Bulging Disc

Bulging Disc Definition

A potentially painful problem in which the hard outer coating of the disk is damaged, allowing the disk’s jelly-like center to leak and cause irritation to adjacent nerves.


You may have been told you have a bulging disc by a doctor, but do you really understand what they just said to you? Let me help explain it in a more simple way so you can try fully understand.

Spinal Disc Anatomy

We have 23 discs in our spines that sit in between 24 vertebrae in our spines.

The only place you don’t have a disc between two vertebrae is right at the top between C1-2.

When a doctor says things like “L4-5, L5-S1 or C5-6” what they are actually saying is where in the spine the disc is bulging or herniated.

  • C – stands for cervical and is the neck part of your spine.
  • T – stands for thoracic and is the upper and middle back.
  • L – stands for lumbar and is your lower back.
  • S – stands for sacrum and is where your tailbone or coccyx area is.

There are 7 cervical, 12 thoracic, 5 lumbar and 1 sacrum bones.

So for example in the lower back L4-5 means the doctor is talking about the disc between the 4th lumbar bone and the 5th lumbar bone. The disc itself is actually called L4-5.

This number system helps doctors and radiologists know where each other is talking about and where the back pain or neck pain is coming from.

Each spinal disc is made up of two parts: 1.Nucleus Pulposus, 2.Annulus Fibrosis.

What is the Nucleus Pulposus?

The nucleus pulposes is the middle part of a back disc. It is like a racket or squash ball in the middle. It is softer than the surrounding annulus fibrosis part. The nucleus pulposus doesn’t have nerves or blood supplying it. So you can’t feel pain directly in the nucleus pulposus. It also can’t heal itself without the process of osmosis.

What is the Annulus Fibrosis?

The annulus fibrosis is the outer part of the disc. It is like the layers of an onion and is the hardest part of the disc in your back. The annulus pulposus does have some nerves supplying the outer part of it but also has no direct blood supply. It is the annulus pulposus that causes the most pain from in a bulging disc or herniated disc.

Did you know that there are different ways to classify a bulging disc? This spinal disc classification system is important not only for the radiologist reporting on your MRI scan, but also for you. The way your disc injury is classified according to the radiologist tells you how bad the disc injury is.

Some people may just call it a ‘slipped disc’, but in reality it could be a herniated disc or bulging disc. Find out today how your radiologist has determined how bad your disc pathology is and which type of disc injury you have.

Common Spinal Areas Affected

Bulging Disc in Low Back & Neck

The most common areas to get a bulging disc in your back are in your lower back and in your neck. Today I want to show you the most common levels in your lumbar spine and cervical spine that tend to cause a bulging disc pain problem. It is amazing how few places out of the 23 discs tend to be a problem.

Bulging Disc in Lower Back

When you have a bulging disc in your lower back it is called a lumbar disc bulge.

The word, lumbar, is the medical term for the 5 lower back bones (vertebrae).

The most common lumbar disc bulging occurs at L4-5 and L5-S1. If you hear someone say they have had a low back surgery and a painful lower back disc, 90% chance if you say “Is it the L4-5 or L5-S1 disc” they will say how did you know.

If your low back disc bulges at L4-5 it can pinch the nerve coming out below it called L5. The L5 nerve root is apart of the major nerve in your leg called your sciatic nerve.

If your low back disc bulges at L5-S1 it can pinch the nerve coming out below it called S1. The S1 nerve root is also apart of the sciatic nerve in the leg running too your feet.

Bulging Disc in Neck

When you have a bulging disc in your neck it is calles a cervical disc bulge.

The word, cervical, is the medical term for the 7 neck bones.

The most common cervical disc bulging occurs at C4-5, C5-6 and C6-7. So you can see there tend to be more places a bulgin disc occurs in the neck compared to the lower back just because there is more movement here and more discs.

If your neck disc bulges at C4-5 it can pinch the nerve coming out there called C4. This nerve goes into your shoulder area.

If your neck disc bulges at C5-6 it can pinch the nerve coming out there called C5. This nerve goes into your shoulder and upper arm.

If your neck bulges at C6-7 disc it can pinch the nerve coming out there called C6. This nerve goes all the way down to the elbow and fingers.

Bulging Disc Symptoms

Here are some of the most common symptoms from a bulging disc:

  1. Low Back Pain or Neck Pain – coming from the pinched nerve, facet joint or muscles
  2. Weakness – from having a pinched nerve or muscle spasm,
  3. Pins and Needles – this could show pressure build up on the nerve root,
  4. Back Stiffness – usually in the morning and could hear clicking with movement,
  5. Sciatica – pain down the back of the leg into the calf muscle,
  6. Arm, Shoulder, Elbow Pain – pain running into the shoulder blade and arm.

So as you can see from the bulging disc symptoms above that the biggest way to know is pain.

Pain is also when most people will see a doctor to diagnose why they have a back, arm or leg pain.

Bulging disc symptoms may start without reason. Bulging disc symptoms may start with simple stiffness in your back, which then progress over time into pain.

Anatomical Sources of Neck & Back Pain

Bulging Disc Symtpoms

So you have a pain in your neck or a pain in your lower back and you might be wondering what are the symptoms of a bulging disc? Today I want to take a look at how you might know the disc in your back is bulging or herniated.

When a disc bulges it can pinch a nerve or irritate the spinal joints called facet joints. If the discs in your back bulge you might lose some height. This process is called degenerative disc disease. I want to take a closer look at the degeneration process at the joints, disc and nerve roots at the spine and what some of the most common symptoms you might here from others with a bulging disc pain.

1. The Spinal Facet Joints

What degenerative disc disease means is that the spinal discs are losing their ability to retain water and heal. So the discs start to degenerate by losing water. This can be seen on a MRI scan of spinal discs. When the disc loses water it loses height. This means the two back bones come closer together.

When the back bones come closer together more pressure is put on the facet joints. There are two facet joints between to vertebrae and they will also start degenerating just like the disc. This process of facet joint degeneration is sometimes called spondylosis, osteoarthritis or degenerative joint disease.

These spinal facet joints have lots of nerve endings around them and in the ligaments surrounding them. So pain can be coming from too much pressure and inflammation on your facet joints.

2. The Disc

The bulging disc causes the outer part of the disc, the annulus fibrosis, to bulge out. This is what is seen when classifying your disc injury on the MRI scan.

There are some nerves in the annulus fibrosis which can send pain signals. Especially if the annulus fibrosis starts to tear. The tear is a sign of more disc degeneration and possibility of a disc herniation.

3. The Nerve Root

The last major part to cause pain from a bulging disc is the nerve leaving the spine called the nerve root.

The nerve root in the lower back might be L5 or S1 in the neck it might be the C4, C5 or C6 nerve roots being pinched.

The pain from a pinched nerve root can be excruciating. Nerve pain is medical known as neuropathic pain and is different from inflammatory pain.

Someone with a pinched nerve in their lower back might get sciatica pain. In the neck a pinched nerve root causes shoulder, elbow and arm pain.

Spinal Disc Injury Classification

MRI Scan For Back Pain

First thing that is needed is a Magnetic Resonance Imaging scan also known as a MRI scan.

These MRI scans are very sophisticated machines using magnet technology to take very detailed pictures of your spine, discs, nerves and muscles. You can see a lot of detail on a MRI scan compared to the traditional x-ray.

Really MRI scans are the gold standard test to see what your the disc in your back or neck looks like.

Here is a great example of a MRI scan of a slipped disc in the neck.

Spinal Disc Nomenclature

It is best to name a disc condition in your lower back or neck as:

  1. Disc Bulge – Bulge is Asymmetric or Symmetric
  2. Disc Herniation – with Protrusion or Extrusion

I know it can seem confusing, but this is how much detail can go into classifying a disc injury in your back.

The spinal disc typically degenerates first and then starts to bulge. This is the process where degenerative disc disease will cause the spinal disc to herniate or bulge.

Again you may be confused asking so do I have a symmetric disc bulge, disc herniation with extrusion?

The main thing is do not worry about the exact disc injury type terminology. This information is more important to a physical therapist, osteopath, chiropractor or spinal surgeon whose care you are under. Even a back disc herniation can be classified as mild, moderate or severe.

Basically for you what is important to know is that a bulging disc is less severe than a herniated disc in your back. Also you’ll want to know if the disc is pinching a nerve leaving your spine which is important as well.

If really need to know and you would like more detail on the in-depth process of working out what the type of spinal disc bulge or spinal disc herniation I can recommend this article “A Synopsis of Nomenclature and Classification of Lumbar Disc Herniation”.