Low Back Pain: Disc Related Pain
Some (not so) cool facts:
Approximately 80% of people will experience low back pain at some point in their lives. In 2020, LBP accounted for 8.1% of all-cause years lived with disability globally.
Factors influencing LBP prevalence:
Age and genetics: The prevalence of LBP increases with age and genetic factors.
Co-morbidities: Being overweight, or having a metabolic, autoimmune, injuries, medical conditions or other diseases
Lifestyle factors: Such as smoking, alcohol consumption, exercise and diet behaviours, sedentary lifestyle, sleep quality,
Occupational factors: Prolonged sitting, heavy lifting, and poor posture can contribute to LBP.
Psychological factors: Stress, depression, and anxiety can exacerbate LBP.
Most of these factors modifiable, which can be changed or controlled through an individuals own actions and lifestyle choices. Non-modifiable factors are variables that you cannot change. There is often multiple factors contributing to LBP that need to be addressed. Often, only one factor is addressed at a time by certain medical or allied health professionals, because health practitioners are trained in their own specialised fields. Personally, I am fortunate enough to have completed a degree in Health Sciences, which covered biology, anatomy, pharmacology, physiology, nutrition, epidemiology, public health, statistics, psychology, health promotion and ethics in healthcare - to name a few. I then had the chance to apply that knowledge in a physiotherapy context. Almost 10 years of learning across a vast majority of health related subjects helps, but it is not the norm. My experiences have led to the creation of BetterU, with the aim to apply a multidisciplinary approach to delivering meaningful and impactful change, by addressing all identifiable factors to achieve the best results for our patients. By working together as a team, we can address health holistically.
Now back to the task at hand. Low back pain, can often present locally, or radiate down either/or legs, and often is felt down the posterior (back) of the leg and into the calf (known as sciatica). A common phrase used for the past decade has been “non-specific low back pain”, which means “we don’t know why it hurts”. But let’s break down the back… So to speak, so we can understand things a little bit more than “non-specific”. The following information may be a little on the heavy side, but patient education is paramount; a well-informed patient has a much improved ability to recover - to quote a wise man: knowledge is power.
Important things to cover are:
Anatomy
Pathophysiology (cause of the pathology)
Treatment and Management Strategies (including surgery vs. conservative/non-surgical options)
Anatomy
Your spine is made up of 33 vertebrae at birth, which technically becomes 26 at maturity, and 23 intervertebral (between vertebrae) discs. There are A LOT of ligaments and muscles, which support the spinal structure. This complex structure allows you to move in many different ways, the spine can twist, bend and rotate - all at once. There are nerves that come out either side of the spine at each level, innervating almost everything in the body, including muscles, bones, organs, blood vessels, skin and other soft tissues such as the discs. An important note is that nerve innervation varies across structures, soft fibrous tissue such as discs and ligaments have less innervation compared to other structures. This will be important for later.
Many of these structures can be the cause of low back pain. Now, before continuing to pathophysiology, it’s important to note that all pain is transmitted through nerves, and nerves themselves are never the cause of LBP, but merely a signalling pathway to inform the brain of a potential sensation. The brain takes the signals, decides what that signal should be interpreted as, and sends the information back, where we then “feel” the pain.
Structures that are culprits of LBP:
Disc
Bone
Muscle
Organ
Tumor
Other - such as scar tissue
Pathophysiology
Disc related low back pain:
Discs are tough fibrous pad-like structures that act as a cushion between the vertebrae bones. They act as shock absorbers, and allow for bending, flexion and rotation of the spinal column. Discs can “pop out” [protrusion], or degrade [degeneration]. It can happen suddenly, or over time. Either way, the cause of disc related back pain is always due to load distribution issues because of insufficient supporting structures.
Going back to the anatomy, the vertebrae is made up of not just bones and discs, but also ligaments and muscles. Ligaments connect bone to bone and help support the structural integrity of the spine. Ligaments are in place to prevent excessive movement of bones only, and are very effective for doing so. They are not so effective in excessive load management. Muscles are the on the front lines for this job. Muscles all work together to help stabilise, move, and distribute load across the spine. If the muscles of the lower back are insufficient, ligaments may take up some of the slack, but very little. Discs are meant to be loaded in a specific way (in the direction of the spinal column). Discs can take a beating, but that’s not really fair for them to take up the slack either. It really is up to the muscles to evenly distribute loads, preventing excessive forces placed on the ligaments and discs.
Ineffective muscles place excessive and uneven load distributions upon the discs, and if the forces are too much for the disc/s and the ligaments to take, one or more of the discs may protrude from its “casing” - colloquially known as a “popped disc”.
The protrusion is not what causes a majority of the pain. Discs are lightly innervated by nerves, and the centre of each disc has no innervation at all. The pain that is experienced following a disc protrusion is due to the pressure and irritation placed on the nerve roots that come out either side of the spinal column at the varying levels.
The order of nerves, for the sake of this blog, begins with the large spinal cord that comes down through the spinal column, at each vertebral level, nerve roots leave the spinal cord. The nerve roots innervate the left and right side of the body which brach off, bit by bit, from larger nerves to smaller nerves; eventually innervating organs, muscles, bones and skin etc. So nerve roots, being close to the spinal column, are easily pressed against by a protruding disc, cause downstream symptoms, such as pain (known as referred pain), pins and needles, numbness and muscle weakness.
The order of nerves can be thought of like a road map, from highways (spinal cord), to main roads (nerve roots), to streets (passing through large organs and muscles) and finally connecting to footpaths (soft tissue, skin, bone, blood vessels etc.). So depending on where the disc is pressing along the road map, will result in various symptoms and pain patterns.
It gets a little trickier from here however. Each nerve root quickly separates, and for arguments sake, should be considered as several highways, that branch off to their own main roads and the like. So depending on what area of the nerve root is being pressed (and by how much), will depend on the downstream symptoms. If a protruded disc is pressing against s specific part of the nerve root, you may experience more localised back pain, extending no further than the hip. Some people may feel pain in the back only, some may feel pain only in the buttock, or the front of their thigh, or in their groin. This is because, that part of the root directly leads to these specific areas. Pain may be experienced below the hip, into the buttock or below the buttock into the hamstring or quadriceps, or may extend even further, down into the calf and/or foot. This is due to more of the nerve root being irritated and more pathways being affected.
Again, it gets a bit trickier. Remember when we discussed that each level of the spinal column having nerve roots that come out from the spinal cord? Well each individual nerve root level is responsible for their own networks and pathways. The level that is associated with sciatic pain (pain through the sciatic nerve which passed through the buttock, hamstring and calf), is different to other levels. This is another reason pain can vary so much between patients. They may have a combination of these pain patterns if there is multiple disc protrusions.
And again, it gets a bit trickier. Discs can be thought of like fluid-filled sacs (their not - technically), but they can move, in terms of the direction and severity of the protrusion. If they push left, left sided symptoms occur, same with the right side. If they push in a more forward direction, it can result in both left and right sided symptoms. They can also shift from one position to another. So symptoms can change from one leg to both and back to one leg again…
Finally, if the irritation of the nerves are enough, symptoms discussed before such as pins and needles and muscle weakness can occur. Muscle weakness is a sign of nerve degeneration, nerves that are irritated enough will begin to degrade, and conduction of signals lowers to the extent that weakness is present in the associated pathways (muscles). Luckily, peripheral nerves (nerves outside of the spinal cord, can regenerate.
All of this may be overwhelming at this point, but let’s go back to the consistent cause of disc protrusions: it is always due to poor load distributions because of weak muscles. So even though different levels cause different symptoms, disc related back pain has the same pathophysiological cause: weak muscles.
Treatment and Management Strategies:
Take control of your health: By focusing on the factors you can change, you can significantly reduce your risk of developing certain health problems.
Make informed decisions: Knowing your non-modifiable risk factors can help you make informed decisions about your health and seek appropriate preventive measures.
Work with your doctor: You can discuss both modifiable and non-modifiable factors with your doctor to create a personalized health plan.
To be completed…
