By Dr Graeme Fitzpatrick, Consultant in Anaesthesia and Pain Medicine
Three assumptions recur across contested pain claims: that a normal scan means the pain isn’t real, that a successful operation should have resolved it, and that pain severity can be read off the medication a claimant is or isn’t taking. Each substitutes an indirect marker for a direct measure of pain, and each can mislead in both directions toward understating a genuine claim and toward overstating one. Understanding why matters as much for a defendant seeking to test a claim as it does for a claimant seeking to prove one.
Introduction
Pain evidence is unusual among medico-legal disciplines in that the thing actually being assessed – the claimant’s subjective experience, cannot be directly observed. That absence creates pressure to substitute something that can be observed: a scan, a surgical outcome, a prescription. Each of those substitutes is useful evidence. None of them is a measure of pain. The distinction sounds academic until it is applied to a report that treats a normal MRI, a technically successful fusion, or a modest medication list as though it settled the question of severity. A proxy that corroborates an assessment is doing legitimate work. A proxy that replaces one is not.
Pain Is Not a Measure of Tissue Damage
The IASP defines pain as an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage – a definition that deliberately does not require demonstrable tissue damage to be present at all. Pain is a biological, psychological and social experience, generated by the brain’s interpretation of threat, not read directly off peripheral injury. Nerves transmit signals; the brain interprets them, and that interpretation is shaped by context, prior experience and psychological state as much as by the injury itself. Injury can resolve while pain persists, just as pain can be entirely absent despite significant identifiable pathology.
This is the conceptual root of why imaging, surgical outcome and medication use each fail as standalone proxies for severity and it is worth being explicit that this is not a claimant-favourable or defendant-favourable starting point. It is simply where the medicine is, and any report that treats one of the three proxies as decisive is asking evidence to answer a question it was never designed to answer.
Why Imaging Can Mislead – In Both Directions
Scans show structure, not sensitivity or function. This is particularly evident when considering spinal MRI scans in the context of chronic back pain. Significant degenerative changes are common in pain-free adults – a well-established finding across the imaging literature (Deyo, Mirza & Martin, 2006; Wang, Videman & Battié, 2012), which means imaging findings often carry limited or no predictive value for pain severity. A mild MRI can coexist with severe pain; a severe MRI can coexist with mild pain.
A normal scan is not evidence that pain is absent. This is the more commonly recognised half of the problem, and it is the one raised most often on a claimant’s behalf.
An abnormal scan is not, by itself, evidence that the index event caused what it shows. This is the less commonly interrogated half, and it matters just as much. Degenerative findings visible on imaging are frequently pre-existing, age-related, and present in asymptomatic individuals; their appearance on a post-incident scan does not establish that the incident caused them, or that they, rather than some other mechanism, are responsible for the reported pain. A report that treats an abnormal finding as self-evidently causative has made the same category error, from the opposite direction, as one that treats a normal finding as self-evidently exculpatory. Imaging cannot quantify pain, function, or credibility, and it cannot, on its own, establish causation either.
Why Surgical Success Doesn’t Guarantee Pain Resolution
Whilst surgery may remove nerve compression or correct a structural lesion; it does not always resolve the nerve injury or central changes that produced the pain in the first place. Where central amplification has already become established, or where neuropathic pain has come to dominate the clinical picture, persistent post-surgical pain is a recognised outcome in its own right – reflected in ICD-11’s classification of Persistent Post-Surgical Pain as a distinct diagnostic entity (Treede et al., 2019), not a residual symptom of incomplete surgery.
Technical success and clinical resolution are not the same event. A surgical note describing an uncomplicated procedure with satisfactory imaging outcome answers a surgical question. It does not answer the separate question of whether the pain-generating process, which may already have shifted from peripheral to central mechanisms by the time surgery took place, has been addressed. Treating the former as evidence against the latter conflates two questions that pain medicine treats as genuinely distinct.
Why Medication Use Is a Poor Proxy – Also in Both Directions
What medication a claimant has received is a decision made by their treating doctor, not the claimant, and analgesic prescribing is in any case an unreliable proxy for pain experience. Opioids are not recommended for long-term pain management given their limited long-term benefit and significant risk of adverse effects (Von Korff et al., 2011; Martell et al., 2007), and the relationship between opioid use and pain severity is further complicated by well-documented patterns of both under- and over-prescribing relative to clinical need (Mazza, Jamison & Edwards, 2018).
Furthermore, high-dose opioid therapy may itself worsen pain through a recognised phenomenon known as opioid-induced hyperalgesia. Where present, this may complicate causal analysis, as the claimant’s pain experience may be influenced not only by the underlying pathology and their psychosocial context, but also by the effects of its treatment.
The absence of strong analgesia is not evidence of the absence of severe pain – it may be entirely appropriate, clinically, for a claimant with significant pain to be taking little or no medication, particularly where opioid use has been deliberately limited on grounds of clinical safety or likely effectiveness. Equally, the presence of strong analgesia is not proof of pain severity either, prescribing decisions reflect clinician judgement, local prescribing culture, and risk tolerance as much as they reflect the claimant’s actual experience. Medico-legal assessment should mirror clinical practice on this point: the focus belongs on function, assessed holistically, not on the medication list.
What This Means for the Expert’s Task
An expert’s overriding duty under CPR Part 35 is to the court, not to the instructing party, and that duty is most tested precisely where a single, easily-cited piece of evidence – a scan report, a discharge summary, a prescription history, could support a quick conclusion. Deferring to any one of these proxies is not independence; it is the appearance of rigour standing in for the substance of it.
The burden remains on the claimant to establish causation and extent of loss on the balance of probabilities, and that burden is not discharged, or defeated, by any single proxy in isolation. Properly weighing pain severity requires triangulating multiple sources: pre-injury state, injury mechanism, pain phenotype, careful clinical examination, functional and psychological impact, and the internal and temporal consistency of the claimant’s account over time. Imaging, surgical outcome and analgesic use can each inform that triangulation. None of them substitutes for it.
A few practical questions follow for anyone assessing or testing a report built substantially on one of these three proxies:
- Does the report treat a scan finding as evidence of pain severity, or only as evidence of structure and does it address whether an abnormal finding is even attributable to the index event?
- Where surgery has taken place, does the report distinguish between technical success and resolution of the underlying pain-generating process?
- Is medication use being used to infer severity in either direction, without acknowledging that prescribing reflects clinical decision-making as much as patient experience?
- Has the opinion been built by triangulating multiple sources of evidence, or does it rest substantially on one proxy that happened to be easiest to obtain?
Conclusion
Scans, operations and prescriptions each answer a narrower question than the one litigation actually asks, and each can mislead by omission in one direction and by overreach in the other. Sound medico-legal opinion on pain severity has to be built from the full clinical picture, not from whichever single proxy happens to be easiest to point to, however persuasive it looks in isolation.
Related Insights: ICD-11 and Chronic Pain in Litigation: Why Classification Matters
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FAQs
- Does a normal MRI mean the pain isn’t genuine? No. Imaging shows structure, not sensitivity or function, and degenerative findings are common in people with no pain at all, a normal scan does not establish the absence of pain.
- Does an abnormal scan prove the pain was caused by the accident or incident? Not on its own. Many degenerative findings are pre-existing and age-related, and their appearance on a post-incident scan does not by itself establish that the incident caused them or that they explain the reported pain.
- Should a successful operation resolve pain? Not necessarily. Surgery addresses the compression or structural lesion, not any nerve injury or central sensitisation that had already become established before the operation.
- Can pain severity be judged by medication use? No, in either direction. Medication is prescribed by the treating clinician based on clinical judgement and safety considerations, so neither low nor high analgesic use reliably indicates the true severity of the underlying pain.
- What should experts rely on instead of these proxies? A combined assessment of pre-injury state, mechanism, pain phenotype, clinical examination, functional and psychological impact, and internal and temporal consistency, with imaging, surgical outcome and medication history used to corroborate rather than substitute for that assessment.
- Is this relevant to both claimant and defendant instructions? Yes. The same principle applies in both directions — a normal scan or successful surgery is not, by itself, evidence against genuine ongoing pain, and an abnormal scan or heavy medication use is not, by itself, proof of it.
