Common causes of lower back pain

Common causes of lower back pain

Written by our new Chiropractor; George Gibson.

With today’s blog being the first of many (I hope) I saw it fitting to touch upon the most common thing that presents to us in clinic; lower back pain. Many of the patients we see have been through a variety of different healthcare professionals by the time they get to us and have never had the injury mechanism explained behind their lower back pain. I wanted to briefly touch on this and some common injuries which occur in the lower back, with the aim to provide widely available information for our patients to understand certain pain triggers and injury mechanisms.

The human spine

The spine is composed of 24 bones called vertebrae, each vertebrae is separated by a flexible intervertebral disc which allows for shock absorption. They are connected via joints at the back of the spine similar to our knuckles in our fingers called “facet joints”, these allow for flexion and rotation type movements of the spine. All these joints and tissues are held together by muscles, ligaments and fascia which provide a balance of both stability and mobility.

Fig.1: The human spine demonstrating the natural lordotic and kyphotic curvatures

 

The spine is arranged in three natural curves; the cervical spine, thoracic spine and lumbar spine, these curves allow for even distribution of forces through the spine opposed to a vertical column. When we stand upright we may imagine that this curvature straightens out but this is not the case; even with “good posture” these curves remain present.

All of the structures in our spine and body have a certain amount of capacity or loading they can tolerate before injury occurs. Pain can often be attributed to overloading or exposing these parts of our anatomy through various day-day movements or stresses which the body is not accustomed to (McGill 2007).  Being able to recognise these painful movements, triggers or overloading capacity is essential for daily pain free activity.

Although there is a lot of debate into the importance of technique and movement among healthcare professionals, full range of motion throughout our lower back is completely normal and promotes healthy tissue. When it comes to movement under heavy load however, we may need to be more aware of the position of our spine. For most people, a neutral position can tolerate and produce more force when moving objects. An untrained spine that buckles under load (when rounding the back occurs during movement of heavy objects off the floor for example) creates an environment for potential injury to occur. Injury essentially occurs when too much force is applied too often or too soon for an individual to tolerate it, each person has different levels of tolerance to loads or compression. Once this barrier has been crossed it can cause pain and lead to intolerance to certain movements or activities.

For some people, repeated flexion movements may actually be a good thing for the spine and surrounding musculature; people may adapt to this movement through gradual exposure over time. This again may vary from person-person based on individual adaptability and lifestyle differences.

People may also experience lower back pain without any damage occurring or even long after tissue healing has taken place we can be left with chronic pain, this is usually when the body becomes sensitised and guarded. We will cover this in a later blog.

Disc bulges and discogenic pain

Many patients I see come in and have either been told or are under the notion they have a “slipped disc”. Discs do not slip, they are far more durable than this and are actually woven into the bone. They are sometimes compared to as jam donuts, this is because the gel like substance in the middle of the disc (nucleus pulposus) can be gradually squeezed out over time. Despite a patient often experiencing a sudden severe onset of pain, they often do not bulge or squeeze out quickly or during one event. It is likely this injury has been an ongoing process, I often make the comparison of disc injury to snapping a credit card. If you try to snap a card, it does not snap in one movement- it requires constant whittling back and forward before it weakens.

Fig.2: Frost et al (2019), Demonstrating disc anatomy

In reality, injuries to discs are much more complex than this. Once the gel like substance in the centre part of the disc has escaped the tough outer collagen fibres of the disc, it can come into contact with a nerve root which can cause various pains moving into the lower limb. Whilst many patients with discogenic injuries may experience pain in leaning forward, it is important to note there are variations to this (Balkovec and McGill 2012).

Fig.3: Dynamic disc designs (2021), spinal unit showing 2 vertebrae, intervertebral disc, nerve roots and spinal cord.

For a patient who experiences pain on bending, one strategy when picking up a heavy object is to aim to keep the spine as “neutral” as possible in order to generate power and keep as much compressive force moving through the midline as possible. This is because the human spine is often compared to a guy wire system where the spine is a flexible rod that is capable of moving in multiple directions. The muscles act as guy wires and stabilize the spine to limit and control the amount of movement in order to prevent injury. Insufficient stiffness of these guy wires can allow the spine to buckle causing pain and occasionally a discogenic injury (McGill, 2018).

Although for some people it is important to aim for a “neutral spine” when lifting heavy objects, it is important not to fear bending or lumbar flexion. For others, moving heavy loads in a more flexed position could be advantageous for them (Mawston et al. 2021).

More research is needed on the topic and each individual will have different tolerances, durability and anatomical variations and as such there is no gold standard for perfect lifting technique.

Stenotic changes

Spinal stenosis is a condition that effects 11% of the population, particularly in the elderly (Jensen et al. 2021). Stenosis is a Greek word that means “to narrow”. Stenosis of the lower back means a decrease in space inside the spinal canal or the intervertebral foramen; this can either be caused by bony arthritis or soft tissue changes such as thickening of ligaments.

Fig.4: Demonstrates the decrease in space in the spinal canal and intervertebral foramen will often cause pain referring down into the leg or weakness of the lower limb.

Similar to disc injuries, as a decrease in space gradually starts to occur either in the central canal or intervertebral foreman. It can compromise either the spinal cord or nerve roots; this can cause pain in the legs, difficulty walking and can limit daily function (Jensen et al. 2021).

Individuals with this condition often complain of difficulty when walking downhill, standing for an extended period of time and often have their symptoms relieved when seated or bending over. A classic presentation of this is the shopping cart sign, when a patient feels a relief in symptoms from leaning forward onto their trolley. All of these movements have one thing in common- extension intolerance. This is due to extension movements further narrowing the space at the back of the spine and increasing an individuals symptoms. For many people, management of stenosis will come through changes in their day-day postures or exercises which improve movement patterns that allow them to maintain function and mobility.

Facet Joint injury

Facet joint injuries affect around 15% of people with chronic lower back pain. As previously mentioned, facets are the small joints on the back of the spine; they facilitate movement and are surrounded by a joint capsule (similar to glove fitting over a hand). This capsule contains a fluid allowing for movement, as well as sensing the position of the joint and dysfunction (pain). In order for it to do this it is innervated by many nerve endings which provide this feedback to the brain to help coordinate movement and process pain (Cohen and Raja 2007).

Fig.5: Demonstrating a facet joint at the back of the spine encircled in red

Similar to discs, facet joint injuries can often occur due to continuous stress or repetitive strain. There is a number of different movements which can cause a facet joint injury, the most common of these is moving in extension (leaning back) combined with rotation. This puts excessive amounts of pressure on the small joints at the back. Although it may feel as there is a sudden “pop” or specific point in which the pain is noticed, it is often due to repetitive movements or over loading long before this.

Although all facet joints are capable of referring pain to the groin, the upper facet joints of the lumbar spine are capable of referring pain into the flank, hip and the side and back of the thigh (Cohen and Raja 2007).  For most people experiencing facet joint pain, they can almost localise a specific position on their back by placing their finger on the area.

Muscular Spasm/Pain

One common complaint I see is patients presenting with “muscular spasm”; a common example of this is extreme pain whilst getting out of a car or seizing up whilst trying to stand up straight. While it is entirely possible to strain a muscle in the lower back, it is more likely due to an underlying cause. All of the aforementioned injury mechanisms can cause muscular pain or spasm. Our bodies have developed a complex mechanism of processing pain and trying to self manage injury. Often, when injury occurs in the lower back, the surrounding musculature will stiffen in an attempt to prevent any further injury (McGill 2007). Whilst this is helpful in the short term, long term these muscles can fatigue, overcompensate and be responsible for pain production themselves.

 

Further Advice 

Whilst there are many other ways to injure the lower back, the conditions in this blog are the most common I see presenting in clinic. There is a multitude of other factors and variations of these injuries, all of which should be approached on an individual basis for each patient. As a general rule of thumb, these conditions are usually approached using a combination of patient education, manual therapy (massage, manipulation, dry needling) and exercise (George et al. 2021). The management of these conditions will depend on a variety of factors; the most important thing is to keep positive and know there is a way out of pain.

Diagnosis of lower back disorders can be challenging because of the overlap of symptoms with other conditions that cause leg or low back pain. This blog should be used as a guide. For further advice of how to manage these conditions in both function and pain relief, you should contact a qualified healthcare professional.

 

References

Balkovec, C. and McGill, S., 2012. Extent of nucleus pulposus migration in the annulus of porcine intervertebral discs exposed to cyclic flexion only versus cyclic flexion and extension. Clinical Biomechanics, 27 (8), 766-770.

 

Cohen, S. and Raja, S., 2007. Pathogenesis, Diagnosis, and Treatment of Lumbar Zygapophysial (Facet) Joint Pain. Anesthesiology, 106 (3), 591-614.

 

Dynamic disc designs., 2021. Professional LxH Dynamic Disc Model – Dynamic Disc Designs [online]. Dynamic Disc Designs. Available from: https://dynamicdiscdesigns.com/product/professional-lxh-disc-model/ [Accessed 21 Oct 2021].

 

Frost, B., Camarero-Espinosa, S. and Foster, E., 2019. Materials for the Spine: Anatomy, Problems, and Solutions. Materials, 12 (2), 253.

 

George, S., Fritz, J. and Silfies, S., 2021. Interventions for the Management of Acute and Chronic Low Back Pain: Revision 2021. Journal of Orthopaedic & Sports Physical Therapy, 51 (11).

 

Jensen, R., Harhangi, B., Huygen, F. and Koes, B., 2021. Lumbar spinal stenosis. BMJ, n1581.

 

McGill, S., 2007. Low Back Disorders. 3rd ed. Champaign, Ill.: Human Kinetics.

 

McGill, S., 2018. Spine flexion exercise: Myths, Truths and Issues affecting health and performance. McGill Articles. Blog.

 

 

 

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