One of the most common things I hear in a clinical setting goes something like this: “The scan is clear. The doctor says everything looks fine. So why does it still hurt?” It is a genuinely difficult question to answer in a ten-minute appointment. And for the person sitting across from me, it can feel deeply invalidating, as though the pain is somehow imaginary, or worse, their fault.
It is not. And the science is clear on that.
Persistent pain, sometimes called chronic pain when it lasts beyond three months, is not simply a signal that tissue is damaged. Pain is far more complex than a straightforward alarm system. In this article, we will look at why pain can continue long after an injury has physically healed, what happens inside the nervous system during that process, and what evidence-based options actually help. This is written for patients, carers, and anyone trying to understand what is happening in their own body.
What Is the Difference Between Acute and Persistent Pain?
Pain serves a purpose. In the short term, what clinicians call acute pain, it is a protective mechanism. You sprain your ankle, the tissues are damaged, and pain signals tell you to rest and protect that area. This is normal. This is healthy.
Acute pain usually resolves as the tissue heals. Most soft tissue injuries heal within six to twelve weeks. Bone fractures, depending on location and severity, typically consolidate within eight to twelve weeks. So by that timeline, the physical structure has largely recovered.
Persistent pain, on the other hand, is pain that continues beyond the expected healing period. It outlives its original purpose. The alarm keeps ringing even though there is no longer a fire.
Chronic Pain: The Numbers
According to the British Pain Society, approximately 28 million adults in the UK live with chronic pain. The World Health Organization recognises it as a major global health burden. In the United States, the CDC estimates that around 20.9% of adults experience chronic pain, with 6.9% reporting high-impact chronic pain that limits daily activity on most days.
These are not small numbers. This is a widespread, clinically significant condition, and it deserves a proper explanation.
The Nervous System: How Pain Actually Works
To understand why pain persists, you first need a basic picture of how pain is produced. And this is where most patient information falls short.
Pain does not come from your tissues. It is created by your brain.
That is not a philosophical statement. It is neuroscience.
Nociception vs. Pain
When you injure yourself, specialised nerve endings called nociceptors detect potentially harmful stimuli, pressure, heat, chemical changes in damaged tissue. These signals travel up the spinal cord and into the brain. The brain then evaluates all available information, the signal itself, your emotional state, your past experiences, your beliefs about the injury, and it decides whether to produce pain.
This process is called nociception (detecting a potentially harmful signal), and it is not the same as pain. Pain is the brain’s output, a protective response, not a passive measurement of damage.
This distinction matters enormously. It explains why two people with identical MRI findings can have completely different pain experiences. It explains why soldiers in combat sometimes do not feel gunshot wounds until the adrenaline fades. Context shapes pain.
Why Pain Persists: The Central Sensitisation Explanation
When pain signals fire repeatedly over a prolonged period, the nervous system begins to change. This is the core mechanism behind most cases of persistent pain.
Central sensitisation is the term clinicians use to describe a state where the central nervous system, the brain and spinal cord, becomes hypersensitive. The volume dial, so to speak, gets turned up. Signals that should feel mild start registering as severe. Areas outside the original injury begin to hurt. Even light touch, a process called allodynia, can become painful.
What Happens Biologically?
Several changes occur in a sensitised nervous system:
- Synaptic strengthening: The connections between pain-signalling nerve cells become more efficient, meaning signals pass through more easily and powerfully.
- Reduced inhibition: The brain has its own natural pain-dampening systems. In central sensitisation, these down-regulating systems become less effective.
- Glial cell activation: Supporting cells in the nervous system called glial cells become activated and release inflammatory chemicals, amplifying pain signals further.
- Cortical reorganisation: With prolonged pain, the brain itself can reorganise, areas associated with pain processing expand, which can increase sensitivity across wider body regions.
Research published in the journal Pain has consistently shown that central sensitisation is a key driver in conditions like fibromyalgia, chronic low back pain, whiplash-associated disorder, and complex regional pain syndrome (CRPS).
Common Conditions Where This Pattern Appears
Chronic Low Back Pain
This is arguably the most studied example. Many people with persistent low back pain show normal or near-normal imaging. In clinical practice, I frequently see patients who have had multiple scans, been told “nothing is structurally wrong,” and yet remain genuinely debilitated.
The evidence strongly suggests that in a large proportion of these cases, the pain has become a nervous system phenomenon rather than a structural one. A 2015 review in The Lancet noted that imaging findings like disc degeneration are found almost as commonly in pain-free adults as in those with symptoms, which tells us that the structure alone does not explain the pain.
Fibromyalgia
Fibromyalgia is a condition characterised by widespread musculoskeletal pain, fatigue, and often cognitive difficulties (sometimes described by patients as “brain fog”). There is no detectable tissue damage. No inflammation showing on standard blood tests. For a long time, this led to patients being dismissed.
The clinical consensus now is clear: fibromyalgia is a disorder of pain processing. The nervous system is amplifying signals that should not be amplified. It is real. It has measurable neurological correlates. And it responds, at least partially, to treatments that target the nervous system rather than the tissues.
Post-Surgical Pain
Some people experience persistent pain after procedures that technically went well. The surgery healed perfectly. The wound closed. And yet, months later, pain remains. This is called chronic post-surgical pain (CPSP) and occurs in an estimated 10-50% of people following common surgeries, with 2-10% experiencing severe, disabling pain.
Risk factors include pre-existing pain sensitivity, high levels of anxiety before surgery, and inadequate pain control in the immediate post-operative period, all of which point toward nervous system factors as much as surgical ones.
The Role of Psychology: Not “All in Your Head,” But Brain Involved
Here is where many patients feel defensive, and understandably so. When a clinician mentions psychological factors in persistent pain, it can feel like they are saying the pain is imaginary or self-inflicted.
It is neither.
The brain is a physical organ. Psychological states have measurable biological effects. Anxiety activates the sympathetic nervous system, raising the body’s threat response and amplifying pain signals. Depression is associated with reduced activity in the brain’s natural pain-inhibiting pathways. Catastrophising, a pattern of thinking where pain is interpreted as the worst possible outcome, has been shown in multiple studies to increase pain intensity and disability.
This does not mean the pain is psychological in origin. It means that the brain and body are deeply connected, and addressing one without the other leaves a significant gap in treatment.
Evidence-Based Approaches to Managing Persistent Pain
Pain Neuroscience Education (PNE)
One of the most significant shifts in physiotherapy practice over the past decade has been the adoption of Pain Neuroscience Education, teaching people with persistent pain about how the nervous system works and why pain does not equal damage. Multiple randomised controlled trials have shown that this approach, when delivered well, reduces pain levels, improves movement, and decreases healthcare utilisation.
Understanding that pain can persist without ongoing tissue injury genuinely changes how people relate to their bodies. It reduces fear. And reduced fear often reduces pain.
Graded Exposure and Movement
Avoiding movement because of pain is understandable. It is also, in many cases, counterproductive. Graded exposure, gently and progressively reintroducing activities that have been avoided, helps recalibrate the nervous system over time. It teaches the brain that movement is safe.
This is not “pushing through.” It is structured, evidence-based rehabilitation guided by a clinician.
Psychological Approaches
Cognitive Behavioural Therapy (CBT) and Acceptance and Commitment Therapy (ACT) have both shown meaningful benefits for people living with persistent pain. These are not alternatives to physical treatment, they work best alongside it.
Medication
In some cases, medications that act on the nervous system, such as low-dose tricyclic antidepressants or gabapentinoids, may be used. These are not painkillers in the traditional sense; they work by modulating how the nervous system processes signals. They come with side effects and are not appropriate for everyone. This is a conversation to have with your GP or pain specialist.
Multidisciplinary Pain Management Programmes
For people with complex, long-standing pain, the most effective intervention is often a multidisciplinary pain management programme (PMP), combining physiotherapy, psychology, occupational therapy, and medical input in a structured format. The evidence supporting these programmes is robust.
Frequently Asked Questions (FAQs)
No. Imaging tells us about structure, not about the state of the nervous system. Pain can be entirely genuine and severely limiting without any visible damage on a scan.
For many people, pain levels reduce significantly with the right treatment. For others, the focus shifts to managing pain effectively and improving quality of life. “Cure” is not always the right framework, meaningful improvement is achievable for most people.
This is often a feature of central sensitisation. As the nervous system becomes sensitised, pain can radiate or appear in new areas. This is a known neurological process, not a sign of new damage.
In most cases, yes, though the type, pacing, and intensity matter. Graded exercise, guided by a physiotherapist who understands persistent pain, is one of the best-evidenced interventions available.
Prolonged rest can actually increase sensitivity in some cases. The nervous system does not always improve with immobility. Gradual, supported movement is often more beneficial than extended rest.
Conclusion
Persistent pain is one of the most misunderstood and undertreated conditions in modern healthcare. The experience is real. The mechanisms are well-documented. And the idea that pain means ongoing damage, that it is simply a broken alarm still going off, is outdated.
If your pain has continued beyond what feels reasonable, and if you have been told structurally that “everything looks fine,” please do not interpret that as nothing being wrong. The nervous system is involved. And that is something that can be addressed.
Consult your GP, a qualified physiotherapist, or a specialist pain clinic for a personalised assessment and management plan.
References
- Dahlhamer J, et al. “Prevalence of Chronic Pain and High-Impact Chronic Pain Among Adults – United States, 2016.” MMWR Morb Mortal Wkly Rep. 2018;67(36):1001-1006. CDC.gov
- Woolf CJ. “Central sensitization: Implications for the diagnosis and treatment of pain.” Pain. 2011;152(3 Suppl):S2-15.
- Brinjikji W, et al. “Systematic literature review of imaging features of spinal degeneration in asymptomatic populations.” AJNR Am J Neuroradiol. 2015;36(4):811-816.
- Macrae WA. “Chronic post-surgical pain: 10 years on.” British Journal of Anaesthesia. 2008;101(1):77-86.
- Sullivan MJ, et al. “The role of pain catastrophizing in the prediction of pain and disability.” Pain. 2001;91(1-2):197-206.
- Louw A, et al. “The efficacy of pain neuroscience education on musculoskeletal pain: A systematic review of the literature.” Physiother Theory Pract. 2016;32(5):332-355.
- Veehof MM, et al. “Acceptance-based interventions for the treatment of chronic pain: A systematic review and meta-analysis.” Pain. 2011;152(3):533-542.
- British Pain Society. “Guidelines for Pain Management Programmes for adults.” 2013 (updated guidance). britishpainsociety.org
