Discs are spongy structures found between the vertebrae of our spines that can bulge and herniate for a variety of reasons. Bulging discs describe the outwards protrusion of the outer layers called the annulus. The inner contents of the disc spill outside during a disc herniation.
What exactly is a bulging disc or a herniated disc?
A bulging disc is defined as when the disc bulges beyond the edges of the spine, whereas a herniated disc is where the inner content of the disc spill from within the disc and leak to the surrounding structures of the spine.
The terms ‘bulging disc’ and ‘herniated disc’ are terms that are frequently used by medical professionals to describe changes in the spine. However, they are sometimes used interchangeably despite being different. These changes can lead to conditions, such as lower back pain and sciatica.
Herniated and bulging discs are often seen on imaging investigations, such as X-rays, MRIs and CT scans. After an image of the spine has been taken, radiologists will use these terms to describe any changes through this region(s).
However, these changes in the spine do not always lead to or cause symptoms. Seeking medical advice from a health professional in conjunction with these imaging results is always advised.
A 'bulging disc' is described as the 'disc tissue extending beyond the edges of the ring apophyses'. Simply put, this is when the disc 'bulges' or expands out from the edges. This is comparable to squeezing a filled water balloon and seeing the liquid bulge out from the elastic. Typically, a bulging disc is less likely to lead to severe spinal symptoms whereas a herniated disc will.
Although similar, a 'herniated disc' is described as the 'localised or displacement of disc material beyond the limits of the intervertebral disc'. During a herniation, the inner contents of the disc begin to spill out beyond the border (annulus). As the inner contents leak out, this can compress the surrounding structures, such as the spinal cord and nerves. If this occurs, such problems as sciatica and referred nerve pain can occur.
Disc herniations can be placed into specific categories, which are listed in progressive severity, including:
Disc protrusion -: The inner contents have begun to protrude outside the disc but have not leaked outside. There is still a larger distance between the outside ring and disc material.
Disc extrusion - The inner contents begin to extend out beyond the disc. While the outer ring has not been breached, the distance from the disc material is now minimal.
Sequestered disc - The inner contents have moved outside of the disc and now exist outside the original ring.
Differences between a Bulging disc vs Herniated Disc
Although these terms may seem similar, a disc bulge is not a form of herniation. These are different terms and should not be used interchangeably. While the disc begins to flatten beyond the edges, the inner contents are not spilling outside. Over time, a bulging disc can become at risk of becoming herniated. Herniated discs are more likely to cause neurological symptoms than a bulging disc as the inner contents begin to compress the nerve structures.
Causes of Bulging and Herniated Discs
Disc conditions, such as bulges or herniations, have similar causes. Examples of causes include:
Age. Over time, degenerative changes of the spine over time causes the disc to dry out, which eventually leads to the breakdown of the outer ring (annulus).
Repetitive bending, twisting and loading of the spine (e.g. lifting weights, manual labour occupations, etc.)
Sudden and forceful movements (e.g. performing heavy deadlifts, car accidents, etc.)
Direct trauma (e.g. collision, falling on the back, etc.)
As noted above, both herniated and bulging discs tend to occur with repetitive strain and degenerative changes. From a clinical perspective, disc herniations are more likely to occur with sudden and forceful movements.
5 Tips for Herniated and Bulging Discs (recommended by a physiotherapist)
Seek medical guidance from a health professional (e.g. physiotherapist, GP, etc.) if you are experiencing issues with lower back pain and/or sciatica. They will be able to assess and diagnose the causes of your symptoms. Getting early treatment is crucial for preventing the worsening of your condition and/or symptoms.
Radiological findings (e.g. X-rays, MRI, etc.) of herniated and bulging discs are not a definitive diagnosis of your lower back pain. These can be regular age-related changes to the disc that occur over time. In fact, many people with bulging and/or herniated discs live without any pain or symptoms. For example, a study conducted by Brinjinki et al. (2015)  found that a high percentage of people without back pain had disc problems as seen on X-ray. It's important to talk to a medical professional (e.g. physiotherapist, GP, etc.) to determine whether these disc changes are related or simply coincidental to your symptoms.
Reduce repetitive or long periods of forward bending. While not always the case, bulging and herniated discs are aggravated by lumbar flexion or forward bending movements. Examples of these types of activities include prolonged sitting or picking heavy items off the ground. Try to avoid or reduce these types of activities, particularly early on.
Managing your weight. Being overweight or obese increases the strain through the lumbar spine. Those suffering from bulging or herniated discs can slow down their recovery if they are too heavy.
Certain types of movements and exercises can help assist pain and improve the speed of recovery. For example, some physiotherapists will prescribe the McKenzie Method exercises to help quickly settle symptoms and pain. These types of rehabilitation movements have been specifically created for spinal conditions, such as disc injuries. Always seek guidance from a physiotherapist before performing these exercises.
Bulging and herniated discs are commonplace on radiological imaging, such as X-ray and MRIs. Whether or not they are related to your symptoms requires further physiotherapy or GP assessment. Even if the imaging matches the clinical presentation, the outlook is generally favourable. A large proportion of disc-related injuries will resolve by themselves over time. Typically, a course of physiotherapy and rehabilitation boost your recovery. However, specialist referrals may be required in certain circumstances.