Pain science has changed substantially over recent decades, and the current understanding explains observations that the simple damage model cannot.
The old model
Tissue damage sends a signal, the brain receives it, and pain is proportional to damage.
Which is intuitive and does not fit the evidence.
Severe injuries occur without pain, and severe pain occurs without identifiable damage, both routinely.
The current understanding
Nerve endings detect potentially damaging stimuli and send signals.
Those signals are modulated at multiple points before reaching the brain.
The brain then produces pain as an output, based on the signals and on context, memory, expectation and perceived threat.
Which means pain is a protective output rather than a damage reading, and it can be produced or suppressed independently of tissue state.
The evidence for modulation
Descending pathways from the brain can amplify or suppress incoming signals.
Which is why soldiers and athletes report no pain from serious injury during the event.
Placebo analgesia is blocked by opioid-blocking drugs, which demonstrates the brain producing genuine analgesia.
Persistent pain
Pain continuing beyond expected healing time.
Understood as involving changes in nervous system processing — increased sensitivity, expanded receptive fields, reduced inhibition.
Which is called central sensitisation, and it means the system has become more efficient at producing pain.
The pain is entirely real. The mechanism is different from ongoing tissue damage.
Why this matters clinically
Treatments targeting tissue in persistent pain frequently fail, because the tissue is not the problem.
Which explains the poor outcomes of some surgical interventions for chronic pain.
Approaches targeting the nervous system — education, graded exposure to feared movement, psychological approaches — have better evidence for persistent pain.
Pain education
Explaining these mechanisms to patients has been studied as an intervention.
Trials find reduced pain and disability, with effects attributed to reduced threat perception.
Which is a striking finding — that explaining how pain works reduces it.
Context effects
Expectation, attention, mood and beliefs all measurably affect pain intensity.
Which is not the same as pain being imaginary, and it is a real property of a system that evolved to protect rather than to measure.
What follows practically
Movement is generally safe even where painful, in the absence of specific warning features.
Hurt does not reliably indicate harm.
And graded return to activity works better than avoidance for most persistent musculoskeletal pain.
New pain, pain with neurological symptoms, pain following trauma or pain with systemic features warrants medical assessment, since acute pain frequently does indicate something requiring attention.
Individual variation
Pain sensitivity varies substantially between people for genetic, developmental and psychological reasons.
Which means comparing your pain to someone else's response to the same injury is not informative.
It also means the same tissue state produces different experiences in different people, which clinicians encounter constantly.
Chronic pain prevalence
Affects a substantial proportion of adults in population surveys, and it is a leading cause of disability globally.
Which makes it a major health issue that receives attention disproportionately low relative to its impact.
Specialist pain services exist and are generally under-resourced relative to demand.
Multidisciplinary treatment
Combining physical, psychological and educational approaches.
Which has the best evidence for persistent pain and is more effective than any single component.
It requires services that are organised to deliver it, which is why availability varies enormously.
Medication in persistent pain
Evidence for long-term opioid use in chronic non-cancer pain is weak and the harms are substantial.
Which has led to substantial revision of prescribing guidance, and to difficulty for people already on long-term treatment.
Any change should be planned with a prescriber rather than attempted independently.
Acute pain
Serves a protective function and generally corresponds reasonably to tissue state.
Which is why new pain warrants attention, and why the reframing above applies primarily to persistent pain.
Distinguishing the two matters, since the appropriate response differs.
What to tell a clinician
Where, when it started, what makes it better or worse, what it feels like, and what you cannot do because of it.
Which is more useful than a rating alone, and functional impact is what treatment aims to change.
Sleep and pain
Poor sleep worsens pain sensitivity, demonstrated experimentally.
Which means addressing sleep is part of pain management, and cognitive behavioural therapy for insomnia has reduced pain in people with both.
Communicating about it
Pain is subjective and cannot be measured externally, which makes description the only available information.
Which is why being disbelieved is a common experience, particularly for conditions without visible findings.
Describing functional impact rather than only intensity generally communicates more effectively.
Phantom limb pain
Pain experienced in a limb that is no longer present, reported by a substantial proportion of amputees.
Which is direct evidence that pain does not require tissue, since the tissue does not exist.
Treatments based on this understanding, including mirror therapy, have been developed and have some evidence.