Differential Diagnosis: Demystifying Disc Bulges
Answer these 6 questions to determine if a disc bulge is the cause of your back pain.
The following is the first in a series of "Differential Diagnosis" articles. The aim of this series is to break down and simplify common spinal pathologies to help you identify the cause of your pain. In clinical practice, time and time again, I see clients who feel hopeless and have resigned themselves to putting up with pain that no one seemed to be able to give them answer for. I don’t want this to be you. Their is a path back to comfort, and the first step is understanding the cause of your pain.
Included in this article:
What is a disc bulge.
What causes a disc bulge.
Who gets disc bulges.
What it feels like to develop a disc bulge.
6 questions you can answer to help determine if a bulge is causing your pain.
Before we begin, I want to highlight that this article focuses on the most common type of disc bulge: a small focal bulge. However, there are three categories of disc bulge which I discuss here. If you believe you suffer from one of the other types of disc bulge, I would love to hear from you and I will make it more of a priority to cover those as well in a future article.
What is a disc bulge?
Our intervertebral discs are made up of an outer ring (annulus fibrosis), that contains a gel like substance within its centre (nucleus pulposus). The annulus is formed by concentric rings of collagen that are woven together to form a biological fabric. This fabric can become weakened causing it to stretch and "bulge" outwards into the spinal canal. If the bulge presses on a nerve root it can cause pain.
The key distinction between a disc bulge and a disc herniation, is that in the case of a bulge the disc annulus remains intact. A herniation occurs when a gap in the annulus opens up and allows the gel substance usually contained to the nucleus to leak out of the disc and into the surrounding area. This generally causes more painful and complex symptoms (but that's a discussion for another article).
What causes a disc bulge?
The biomechanical cause of a disc bulge almost sounds too simple for a condition that so many people struggle with and that therapists often have such difficulty identifying accurately and treating appropriately.
A disc bulge is caused by repeated bending under load.
I break down exactly what this means in my article here. The linked article will provide you with a practical understanding of the anatomy of a disc and the mechanical influences that lead to a disc bulge occurring. In clinical practice, I tend to observe that the more a person understands about the nature of their injury, the more empowered they become to take the appropriate steps to heal. If you have a disc bulge, taking the time to read that article will be worthwhile to support your recovery.
Briefly, when we apply repeated strain to our disc annulus, the collagen fibres begin to separate. This weakens the overall structure and allows it to stretch and bulge.
(Again, if you really want to understand this process, read this article.)
BONUS INFO: If the fibres separate too much a big enough gap will open and allow the nucleus to leak through and out of the disc - a disc herniation.
Who gets disc bulges?
Age is a factor in the type of back injuries people are susceptible to. Disc related injuries are more common among younger and middle-aged people. Elderly populations tend to suffer from arthritic and stenotic conditions more commonly, however.
Individual anatomy also plays a role. It’s no accident that 16 year old girls make the best gymnasts but you would never see them in a powerlifting competition. Similarly, try to imagine a 250 pound powerlifter doing a floor routine. It just wouldn’t work. Different people do indeed have different capacities for bending. One reason for this the variation in the shape of our discs.
The disc of a gymnast tends to be more oval in shape where a powerlifters is more limacon (kidney shaped). The disc of a powerlifter tends to become stressed much more easily with bending movements whereas the disc of a gymnast can tolerate lot’s of bending.
We all have individual and genetic variabilities that influence how prone we are to developing a particular injury or illness. However, anyone regularly engaging in the causative mechanism of repeated bending under load could develop a disc bulge eventually. There is generally two patterns commonly observed in the onset of disc bulge related pain.
The first is a slow onset that builds up and gets worse over time. This is seen in people that engage in chronic spine flexion (forward bending) postures over a longer period of time. An example of this would be an office worker that sits hunched at a desk all day. They don't necessarily need to be bending over and picking up heavy things. Simply sitting with a flexed spine over a long period of time can lead to the weakening of our disc annulus causing it to bulge.
The second pattern of onset is more sudden. These are the people that experience a sharp "stabbing" pain that began abruptly when bending forward. When we perform bending movements in our spine under a greater amount of load, it takes less time for our disc annulus to weaken. Some people may develop a disc bulge from a single event. For example, a weightlifter might lose form while going for a personal best on a heavy lift. The additional load on their spine from the weight could cause the annulus to weaken and develop a bulge very quickly.
You may identify more with one of these patterns or may be some combination of the two. An office worker may be gradually weakening their annulus without having any symptoms to make them aware of the changes that are occurring. Then one day they bend over to tie their shoes and get a sudden sharp pain in their back. It wasn't just the act of bending over to pick up the pencil that caused their injury. But rather the progressive damage to their disc that occurred over a long period of time that they didn't notice until performing a certain bending activity, and a bulge developed that caused pain. In other words, it was "the straw that broke the camel's back".
FUN FACT: Disc bulges don’t always cause pain. Some studies analysing MRI finding has estimated that somewhere between 10-30% of the population are walking around with asymptomatic disc bulges.
The common patterns of a disc bulge
People with the same injury tend to have similar experiences with their symptoms. Individual variability does of course exist. However, there are some targeted questions that can be asked to determine the injury a person likely has. I am going to break down 6 of these questions and the answers people with disc bulges tend to give. You can compare this to your own experience to either increase or decrease the likelihood that what you are experiencing is a disc bulge.
1. Does the pain increase or decrease with fast walking?
People with disc injuries tend to have less pain when walking quickly compared to walking slowly.
When we walk quickly and swing our arms, the compressive load on our spines is lessened. This is usually beneficial for people with disc injuries. Other conditions such as stenosis generally don't experience this same benefit. Walking for them will become progressively more painful regardless of the walking speed.
2. Does the pain change with different movements and postures?
People with disc bulges will tend to experience variability in their symptoms with different movements and postures. You may find certain positions to lay in that lead to a reduction in the radiating symptoms going down your legs, for example.
Conversely a certain activity you perform or a posture like bending forward may increase your symptoms and increase the radiating symptoms down your leg.
3. Is your pain aggravated by forward bending activities such as slouched sitting, gardening, cycling, vacuuming, sneezing?
Carrying on from the above question. It is most common for disc bulges to be aggravated by spine flexion postures. If your symptoms are uniquely aggravated by activities that involve flexion postures there is a good chance a disc injury is involved.
4. Does the pain come and go? How long does an acute episode last?
Some people with disc bulges will go extended periods without any pain. They may have recurring episodes of acute back pain.
An acute episode of a bulging disc often triggers an inflammatory process that lasts about 2 weeks.
5. Do you ever step down an uneven section of ground and get a painful "catch" in your spine?
Over time its common for people with disc bulges to lose some height in their disc. This leads to some instability at that level in your spine when performing certain activities that can cause pain.
People with more acute disc bulges may not have lost any height in their disc and therefor not experience any instability related symptoms.
6. Where is the pain located? Is their any radiating symptoms?
Pain usually is usually present in the lower back, however can also cause radiating symptoms across the back, into the groin, down the buttock, or down the legs. An example of these radiating symptoms being the common sciatica symptoms people experience.
Wrapping up
I hope you have found this article insightful to assist in identifying the cause of your back pain. What were your answers to the questions? Is there anything that stood out or something you would like to clarify? Please let me know in the comments!
If you know someone that thinks they have a disc bulge, send them this article and see how they answer the 6 questions.
If you're on the journey to overcoming disc bulge discomfort, you're not alone. Make sure you subscribe so together, we can navigate the path to a stronger, healthier back.
And if the explanations provided in this article don't seem to fit the pattern of your pain then stay tuned or future articles in this series covering other causes of back pain. Comment with the injury you would like covered next!