Back Pain – A Mechanical, but Often Multifactorial Problem

Back pain can have many causes. Most cases are mechanical in nature, involving the spinal joints, intervertebral discs, or the vertebrae themselves. However, pain can also arise from non-spinal structures such as the kidneys, uterus, bladder, or blood vessels, which can sometimes mimic spinal pain (Henschke et al., 2009). Increasingly, research has shown that back pain isn’t always purely structural. In some cases, central sensitisation where the nervous system becomes hypersensitive, leading to pain that persists even after tissues have healed (Nijs et al., 2021). Psychosomatic influences, emotional stress, and lifestyle factors are also now recognised contributors.

Modern understanding has therefore shifted towards a biopsychosocial model, recognising that back pain is influenced by a combination of physical, psychological, and social factors rather than being explained by a single anatomical problem (Hartvigsen et al., 2018). This broader approach explains why two people with similar imaging findings can have very different pain experiences. This is why a thorough assessment is essential not only to identify the physical source of pain but also to consider the wider context.

Patients often describe discomfort in the centre of the lower back or localised to one side, and it is also common for pain to radiate into the buttocks. This happens because many spinal structures are capable of referring pain into nearby regions (Bogduk, 2009). Even everyday activities such as lifting, sneezing, twisting, or sleeping awkwardly can trigger an episode. In more acute cases, people may find themselves bent forward and unable to straighten up.

Here, we’re going to look more closely at some of the main mechanical reasons for lower back pain—focusing on the facet joints, intervertebral discs, and vertebral endplates (Modic changes), Please see the separate Tabs below to better understand why they are such frequent sources of Pain.

References

Bogduk, N. (2009) On the definitions and physiology of back pain, referred pain, and radicular pain. Pain, 147(1–3), pp.17–19.

Hartvigsen, J., Hancock, M.J., Kongsted, A., Louw, Q., Ferreira, M.L., Genevay, S., Hoy, D., Karppinen, J., Pransky, G., Sieper, J. and Smeets, R.J. (2018) ‘What low back pain is and why we need to pay attention’, The Lancet, 391(10137), pp.2356–2367.

Henschke, N., Maher, C.G., Refshauge, K.M., Herbert, R.D., Cumming, R.G., Bleasel, J., York, J., Das, A., McAuley, J.H. (2009) ‘Prevalence of and screening for serious spinal pathology in patients presenting to primary care settings with acute low back pain’, Arthritis & Rheumatism, 60(10), pp.3072–3080.

Nijs, J., George, S.Z., Clauw, D.J., Fernández-de-Las-Peñas, C., Kosek, E., Ickmans, K., Fernández-Carnero, J., Polli, A. and Malfliet, A. (2021) ‘Central sensitisation in chronic pain conditions: latest discoveries and their potential for precision medicine’, The Lancet Rheumatology, 3(5), pp.e383–e392.

Discogenic Pain
Each spinal disc has a tough outer ring (the annulus fibrosus) and a jelly-like centre (the nucleus pulposus) that acts not only as a shock absorber but also as a piece of scaffolding, keeping the vertebra above from compressing directly onto the one below. When this outer ring becomes overstretched or torn, often through lifting, twisting, or trauma, it can cause pain and protective muscle spasm. In some cases, the inner material bulges out and presses on nearby nerves. This can lead to symptoms such as sciatica, where pain radiates from the lower back down the leg, or in the case of the neck, radiates into the arm (Freemont, 2009).

As we age, spinal discs naturally begin to dehydrate and lose height—a process similar to a sponge drying out. This age-related change, often referred to as spondylosis, is frequently symptom-free in many people. However, in others, this reduction in disc volume can cause the vertebrae to sit closer together, leading to joint compression, instability, or nerve irritation (Brinjikji et al., 2015).

A helpful way to visualise this is to think of your spinal discs like the suspension system of a car. When the suspension is healthy, the ride is smooth, absorbing every bump in the road. But when it wears out or loses tension, the ride can become unstable and uncomfortable.

In a similar way, degenerated or worn discs can reduce your spine’s ability to absorb shock, resulting in discomfort, stiffness and pain, this would be classed as “discogenic pain.” If the disc has a slight bulge, compression of a local nerve may occur, potentially leading to sciatica (Jensen et al., 2019). If the disc completely fails to absorb forces, increased stress occurs in the adjacent vertebral bone, leading to inflammation known as Modic Type I bone oedema (Herlin et al., 2018).

References

• Brinjikji, W., Luetmer, P.H., Comstock, B., Bresnahan, B.W., Chen, L.E., Deyo, R.A., Halabi, S., Turner, J.A., Avins, A.L., James, K. and Wald, J.T., 2015. Systematic literature review of imaging features of spinal degeneration in asymptomatic populations. AJNR American Journal of Neuroradiology, 36(4), pp.811-816.

• Freemont, A.J., 2009. The cellular pathobiology of the degenerate intervertebral disc and discogenic back pain. Rheumatology, 48(1), pp.5-10.

• Herlin, C., Kjaer, P., Espeland, A., Skouen, J.S., Leboeuf-Yde, C. and Karppinen, J., 2018. Modic changes—Their associations with low back pain and activity limitation: A systematic literature review and meta-analysis. PLoS One, 13(8), p.e0200677.

• Jensen, R.K., Leboeuf-Yde, C., Wedderkopp, N. and Sorensen, J.S., 2019. Is the presence of a lumbar disc herniation associated with low back pain in adolescents? A prospective cohort study. BMC Musculoskeletal Disorders, 20(1), p.110.

Vertebral Oedema (Modic Type I Changes)
Less commonly discussed, but increasingly recognised, is vertebral oedema, also known as Modic Type I changes. These appear on MRI scans as inflammation within the vertebral bone and are strongly associated with degenerative disc disease. When a disc loses its ability to absorb load, excess stress is transferred to the adjacent vertebrae, triggering inflammation and bone marrow swelling. Over time, this persistent fluid disrupts the inner structure of the bone (Herlin et al., 2018).

To understand this better, it helps to visualise the inside of bone. It is not solid, it’s made up of fine, hair-like structures called trabeculae, which form a mesh-like scaffolding. If fluid or inflammation sits within this delicate network for weeks, months, or even years, it can soften and weaken the structure. The vertebra becomes less capable of handling normal stress, and pain may result from even minor movement or loading (Jensen et al., 2008).

A helpful analogy is to think of a crispy roasted potato fresh from the oven. If you place it in a cup and pour gravy over it, then leave it for an hour or two, the outer crispiness and inner potato soften, turning into mush and losing its form. The same can happen to the vertebrae, constant fluid exposure weakens the internal support, making it more sensitive and vulnerable to pain.

Although still under active research, Modic Type I changes are increasingly recognised as a distinct and treatable cause of chronic back pain (Kjaer et al., 2006; Herlin et al., 2018). Encouragingly, these changes can repair over time, often progressing to Modic Type II, characterised by fatty infiltration, and eventually to Modic Type III, where sclerosis of the vertebrae occurs (Bråten et al., 2019).

References

• Bråten, L.C.H., et al., 2019. Efficacy of antibiotic treatment in patients with chronic low back pain and Modic changes (the AIM study): double blind, randomised, placebo controlled, multicentre trial. BMJ, 367, l5654.

• Herlin, C., Kjaer, P., Espeland, A., Skouen, J.S., Leboeuf-Yde, C. and Karppinen, J., 2018. Modic changes—Their associations with low back pain and activity limitation: A systematic literature review and meta-analysis. PLoS One, 13(8), p.e0200677.

• Jensen, T.S., Karppinen, J., Sorensen, J.S., Niinimäki, J. and Leboeuf-Yde, C., 2008. Vertebral endplate signal changes (Modic change): a systematic literature review of prevalence and association with low back pain. European Spine Journal, 17(11), pp.1407-1422.

• Kjaer, P., Korsholm, L., Bendix, T., Sorensen, J.S., Leboeuf-Yde, C. and Leboeuf-Yde, C., 2006. Modic changes and their associations with clinical findings. European Spine Journal, 15(9), pp.1312-1319.

The facet joints are small stabilising synovial joints at the back of the spine, linking one vertebra to the next and guiding movement, particularly in bending and twisting. Over time, repetitive strain, poor posture, or trauma can cause these joints to enlarge, degenerate, or become inflamed. This can lead to stiffness and localised back pain, which may also radiate into the buttocks or thighs.

Think of the facet joints like the hinges on a door: when they’re well-aligned and lubricated, the door moves freely; when worn or irritated, they creak, stick, and put strain on the frame. Similarly, when facet joints become inflamed or overloaded, movements such as extension, rotation, or initiating flexion often become painful.

Facet joint–related pain is typically mechanical in nature. It often worsens after periods of inactivity or prolonged rest and can ease with gentle movement (StatPearls, 2025). It is also frequently seen in combination with disc degeneration, as both conditions often coexist in spinal osteoarthritis or age-related spondylosis (Cohen et al., 2020).

Research has shown that facet joints contribute to between 15% and 45% of chronic low back pain cases, making them a significant but sometimes overlooked cause of spinal pain (Friedly et al., 2019; Manchikanti et al., 2020). Despite this, diagnosis can be challenging, as symptoms and imaging findings alone are not always reliable. Instead, medial branch blocks or diagnostic nerve injections remain the gold standard for confirming facet-mediated pain (Falco et al., 2020).

Facet joint degeneration is strongly associated with age, particularly after 50, and is more common where disc degeneration is already present (Boateng et al., 2023). Understanding the interplay between discs, joints, and surrounding spinal structures is therefore essential for accurate diagnosis and effective treatment.

References

• Boateng, K.A., Ampomah, K., Baidoo, P.K., Osei, L.B. and Osei-Poku, F., 2023. Lumbar facet joint arthrosis on magnetic resonance imaging and its association with low back pain in a selected Ghanaian population. Journal of Neurosciences in Rural Practice, 14(4), pp.511–517.

• Cohen, S.P., Raja, S.N. and Lamer, T.J., 2020. Pathogenesis, diagnosis, and treatment of lumbar facet joint pain. Anesthesia & Pain Medicine, 15(3), pp.235–248.

• Falco, F.J.E., Manchikanti, L., Datta, S., Sehgal, N., Geffert, S. and Singh, V., 2020. Systematic review of diagnostic utility and therapeutic effectiveness of lumbar facet joint interventions. Pain Physician, 23(6), pp.E557–E590.

• Friedly, J.L., Comstock, B.A., Turner, J.A. and Heagerty, P.J., 2019. Long-term effects of repeated injections for lumbar facet joint pain. Annals of Internal Medicine, 171(7), pp.441–450.

• Manchikanti, L., Kaye, A.D., Soin, A., Albers, S.L., Beall, D.P., Latchaw, R.E. and Hirsch, J.A., 2020. Facet joint pain and its management: a review of current evidence. Pain Physician, 23(6), pp.E557–E590.

• StatPearls, 2025. Facet Joint Disease. [online] Available at: https://www.ncbi.nlm.nih.gov/books/NBK541049/[Accessed 28 August 2025].

While discs, facet joints, and vertebral changes account for much of the back pain we see, there are many other potential causes. These include autoimmune and inflammatory conditions, sacroiliac joint dysfunction, spinal cysts, ligament injuries, fractures, and even psychological or stress-related influences. Rather than listing every possible complexity, the important message is that back pain has many layers and requires careful assessment to identify the true source. At The Injury Hub, we are experts in recognising and managing all of these causes. Our approach combines specialist hands-on care with evidence-based rehabilitation, because research consistently shows that progressive strength and conditioning is the most effective long-term treatment for spinal pain (Saragiotto et al., 2019; Hayden et al., 2021; O’Keeffe et al., 2020). With tailored programmes delivered by our in-house strength and conditioning coach and close collaboration with our spinal specialists, we help patients achieve both immediate relief and lasting resilience. And, if further intervention is required, we have strong links with some of the UK’s leading spinal and orthopaedic surgeons, ensuring rapid access to advanced imaging, targeted injections, or surgical opinion when necessary. Whatever the cause of your back pain, you can be assured that you are fully covered at The Injury Hub.

References

• Saragiotto, B.T., Maher, C.G., Yamato, T.P., Costa, L.O.P., Menezes Costa, L.C., Ostelo, R.W. and Macedo, L.G., 2019. Motor control exercise for chronic non-specific low-back pain. Cochrane Database of Systematic Reviews, (8).

• Hayden, J.A., Ellis, J., Ogilvie, R., Malmivaara, A., van Tulder, M.W. and Henschke, N., 2021. Exercise therapy for chronic low back pain: an updated systematic review and meta-analysis. Cochrane Database of Systematic Reviews, (9).

• O’Keeffe, M., Hayes, A., McCreesh, K., Purtill, H. and O’Sullivan, K., 2020. Are group-based and individual physiotherapy exercise programmes equally effective for chronic low back pain? A systematic review and meta-analysis. British Journal of Sports Medicine, 54(13), pp.798-805.

Sciatica is a condition characterised by altered sensation along the path of the sciatic nerve. This can present in a variety of ways including pain, numbness, pins and needles, electric shooting sensations, or a heavy, aching feeling. These symptoms typically affect one side of the body and follow the course of the sciatic nerve, which travels from the lower back through the buttocks and down the back of the leg, sometimes as far as the foot.

There are many causes of sciatica. One of the most common is a protruded or extruded spinal disc, often referred to as a “slipped disc”, which can press on one of the five nerve roots that contribute to the sciatic nerve. Another common cause is narrowing of the spinal canal (spinal stenosis) or the exit foramina due to bony changes, such as those caused by arthritis. These structural changes can compress the nerves and lead to the familiar symptoms of sciatica (Kwon et al., 2022).

Patients often describe symptoms that begin in the lower back and travel through the buttock, the back of the thigh and calf, and occasionally into the foot. These may range from mild discomfort to severe, sharp, burning, or shooting pain. In some cases, individuals also experience muscle weakness or difficulty with leg control.

However, not all leg symptoms are due to compression of the sciatic nerve itself. Pain can also be referred from spinal discs or joints, what’s known as somatic referral. Research has shown that these structures can mimic sciatica by referring pain into the buttock, thigh, and even as far as the ankle. In these cases of “pseudo-sciatica,” symptoms often do not travel below the knee and are typically more diffuse (Jin et al., 2023).

Deep Gluteal Syndrome

Deep gluteal syndrome refers to irritation or compression of the sciatic nerve caused by soft tissues or bony structures within the hip and pelvis, rather than from the spine. Beneath the larger buttock muscles lies a space occupied by several smaller muscles, including piriformis and quadratus femoris. This condition is relatively underdiagnosed and is characterised by pain and altered sensation in the buttock, hip, and back of the leg. These symptoms can stem from sciatic nerve irritation, but unlike classic sciatica caused by spinal pathology, deep gluteal syndrome typically results from one of two main conditions (Park et al., 2020; Hu, 2021; Külcü et al., 2024).

Piriformis syndrome
In some individuals, the sciatic nerve passes through or alongside the piriformis muscle in the buttock. When the piriformis contracts or becomes tight, it may irritate the nerve and trigger sciatica-like symptoms. However, this condition is relatively rare. At The Injury Hub, we have assessed many patients with sciatica using ultrasound and have rarely found piriformis syndrome to be the sole cause of symptoms. Unfortunately, online searches often overemphasise piriformis syndrome as a common cause of sciatica, which can be misleading. If you’ve been diagnosed with piriformis syndrome without any imaging, we strongly recommend treating that diagnosis with caution until confirmed with appropriate investigations, such as MRI (Hopayian, 2023).

Ischiofemoral impingement syndrome
This is another rare but potentially more likely cause of sciatic nerve irritation than piriformis syndrome. It occurs when there is narrowing at the back of the hip, often due to individual bony architecture, which compresses the quadratus femoris muscle. If this muscle becomes irritated or swollen, it can impinge on the sciatic nerve, resulting in gluteal and leg symptoms (Sun et al., 2023).

References

• Hopayian, K., 2023. Conservative and surgical treatments for piriformis syndrome: a systematic review. Journal of Hip Preservation Surgery, 10(3), pp.255–266.

• Hu, Y-W.E., 2021. Deep gluteal syndrome: A pain in the buttock. Current Sports Medicine Reports, 20(6), pp.279–285.

• Jin, Q., Luo, L., Liu, Z. et al., 2023. Referred pain: characteristics, possible mechanisms, and clinical implications. European Review for Medical and Pharmacological Sciences, 27(8), pp.3272–3280.

• Külcü, D.G., et al., 2024. Deep Gluteal syndrome: An underestimated cause of non-discogenic sciatica. Pain Medicine, 25(1), pp.88–99.

• Kwon, J.W., Moon, S-H., Park, S-Y., Park, S-J., Park, S-R. and Kwon, S-H., 2022. Lumbar spinal stenosis: Review update 2022. Asian Spine Journal, 16(6), pp.834–846.

• Park, J.W., et al., 2020. Deep gluteal syndrome: an emerging cause of non-discogenic sciatica. Skeletal Radiology, 49(11), pp.1741–1752.

• Sun, G., et al., 2023. Arthroscopic treatment of deep gluteal syndrome: clinical outcomes and prognostic factors. BMC Musculoskeletal Disorders, 24(1), p.312.

References

• Saragiotto, B.T., Maher, C.G., Yamato, T.P., Costa, L.O.P., Menezes Costa, L.C., Ostelo, R.W. and Macedo, L.G., 2019. Motor control exercise for chronic non-specific low-back pain. Cochrane Database of Systematic Reviews, (8).
• Hayden, J.A., Ellis, J., Ogilvie, R., Malmivaara, A., van Tulder, M.W. and Henschke, N., 2021. Exercise therapy for chronic low back pain: an updated systematic review and meta-analysis. Cochrane Database of Systematic Reviews, (9).
• O’Keeffe, M., Hayes, A., McCreesh, K., Purtill, H. and O’Sullivan, K., 2020. Are group-based and individual physiotherapy exercise programmes equally effective for chronic low back pain? A systematic review and meta-analysis. British Journal of Sports Medicine, 54(13), pp.798-805.