Causation in Chronic Pain Claims: Distinguishing Physiological Evidence from Prognosis

In personal injury and clinical negligence litigation, claims involving persistent, non-specific pain present significant challenges in distinguishing between objective physiological pathology and clinical prognosis. Establishing legal causation requires an expert to bridge the gap between a demonstrable index event—such as a traumatic injury or surgical complication—and the subsequent development of a chronic pain syndrome. In cases where the pain presentation may appear disproportionate to observable anatomical findings, the reliability and methodology of expert evidence are critical.

The Clinical and Legal Challenge of Chronic Pain

Chronic pain is often characterised by its duration, which may exceed the expected healing window for an acute injury. From a clinical perspective, identifying whether such symptoms are the direct consequence of the index event or the manifestation of a secondary, idiopathic process is a frequent source of contention. The instructing solicitor must ensure that expert evidence addresses both the “but-for” test of factual causation and the legal framework of scope of duty as articulated in Khan v Meadows [2021] UKSC 21. If clinical evidence does not provide a clear structural explanation for the patient’s symptoms, the expert may be required to articulate the distinction between organic pathology and central sensitisation or pain-processing disorders. In this context, solicitors may review complex pain and CRPS indicators to assist in refining the scope of expert instruction, ensuring that the evidence remains robust under cross-examination.

The Role of Multi-Disciplinary Expert Evidence

Chronic pain often involves overlapping systems, which may require input from pain management consultants, neurologists, psychiatrists, or orthopaedic surgeons. A potential pitfall in litigation is the failure to instruct the appropriate subspecialist from the outset. Where a patient exhibits features of both somatic injury and psychological trauma, a single-specialty approach may omit crucial diagnostic considerations. Under CPR 35.3, the expert’s overriding duty is to the court, and this duty is most effectively discharged when the expert’s field of expertise aligns precisely with the clinical issues at hand. When claims span multiple medical disciplines, matched subspecialists are generally better positioned to participate in meaningful expert discussions and joint statements that withstand judicial scrutiny.

Structuring Expert Instructions

• Define the specific clinical issues requiring expert opinion, rather than requesting a general prognosis.
• Ensure the chosen expert possesses the relevant subspecialty accreditation for the specific pain pathology claimed.
• Request that the expert differentiates between pre-existing morbidity and trauma-related symptomology.
• Confirm that the expert is familiar with the requirements of CPR 35.10 regarding report content.

Prognosis and the Scope of Causation

Distinguishing between the physiological evidence of an injury and the projected prognosis is essential for accurate quantum assessment. Experts are often required to distinguish between the primary injury and late-onset complications. Where the defendant disputes the claimant’s ongoing symptoms, the expert evidence must provide a clinical rationale that accounts for both the physical findings and the patient’s individual trajectory. This often necessitates a longitudinal review of clinical records to identify any intervening factors that may have influenced the outcome. Opinions on prognosis should be rooted in evidence-based medicine and reflect the uncertainty inherent in chronic conditions. Solicitors should seek reports that explicitly state the methodology used to assess future prognosis, ensuring that assumptions about future treatment or disability are documented and defensible.

Procedural Considerations for Solicitors

When preparing instructions, solicitors should identify whether the case requires a screening report to determine if causation is capable of being established. If the claim proceeds, the instruction of experts should be proportionate to the issues in dispute. In cases where the parties agree on a neutral expert, the court may direct that evidence be provided by a single joint expert under CPR 35.7, with instructions governed by CPR 35.8. However, in cases of fundamental disagreement on clinical diagnosis, separately instructed experts are often necessary. In such instances, the use of CPR 35.12 discussions and the resulting joint statements are crucial for narrowing the issues for the court. Clear instruction of the correct subspecialist at the outset of the claim significantly reduces the need for costly addendum reports and ensures that the evidence provided to the court is both comprehensive and technically sound.