The expert must distinguish between the underlying condition and the additional harm caused by the accident. A pre-existing problem does not prevent a valid claim, but it may limit the period or extent of symptoms attributable to the event.
Establishing the Pre-Accident Position.
The starting point is the claimant’s condition immediately before the accident. The expert should consider whether the claimant was symptom-free, experiencing occasional symptoms, receiving treatment or already subject to functional restrictions.
A condition may appear on scans or in records without causing symptoms. Degenerative changes in the neck or back may have had no practical effect before the accident. The expert should not assume that the claimant was disabled merely because an abnormality existed.
Equally, a claimant who describes being completely well may have a documented history of consultations, medication, physiotherapy or absence from work. Any difference between the account and the contemporaneous records should be addressed to establish a reliable baseline.
What Does Aggravation Mean?
An aggravation occurs when an accident worsens an existing condition rather than producing a separate one. The worsening may involve greater pain, more frequent symptoms, reduced movement, additional treatment or increased restriction in daily life.
An aggravation may be temporary. A claimant with occasional lower-back pain may experience worse symptoms for six months after a collision before returning to the previous level. The accident may then be responsible for that additional period, but not for the underlying back condition.
An aggravation may also be permanent. A previously stable condition may deteriorate and fail to return to its earlier baseline. The expert must explain why the accident produced a lasting change rather than merely coinciding with the condition’s natural development.
The report should identify what changed, how long the change lasted and what evidence supports the conclusion.
Acceleration Is Different From Aggravation.
An accident may bring forward symptoms that would probably have developed in any event. This is often described as acceleration.
A claimant may have previously asymptomatic spinal degeneration. The expert may conclude that the accident triggered symptoms earlier than they would otherwise have appeared. The accident did not create the degeneration, but it altered the timing of its clinical effect.
Where medically possible, the expert should estimate when symptoms would probably have emerged without the accident. This may be expressed as a period of acceleration rather than attributing all future symptoms permanently to the event.
The estimate should consider the condition, age, previous episodes, imaging, work demands and expected natural progression. A precise period should not be selected simply because it is convenient for valuation.
Causation Requires More Than Timing.
Symptoms beginning or worsening after an accident may support causation, but timing alone is insufficient. The expert should consider whether the mechanism could produce the reported worsening, whether the onset was clinically plausible and whether another event provides a better explanation.
The course of symptoms is also important. Immediate worsening followed by improvement may support a temporary aggravation. A symptom-free interval followed by later deterioration may be harder to attribute to the accident without further explanation.
Practice Direction 35 requires experts to give independent and objective opinions, consider all material facts and address matters that may detract from their conclusions. The report should therefore consider evidence both supporting and weakening the proposed connection.
Medical Records Are Often Essential.
Medical records may show the severity of earlier symptoms, previous treatment, medication, investigations, work absence and functional restrictions.
They may also reveal whether the claimant returned to the pre-accident baseline before a later recurrence. If so, the later symptoms may require another explanation. Continuous post-accident attendance may instead support the view that the condition was materially worsened.
The Personal Injury Pre-Action Protocol promotes the exchange of relevant information and medical evidence. In an aggravation case, an incomplete history may prevent the expert from separating the accident’s effects from the underlying condition.
Avoiding an All-or-Nothing Opinion.
A condition does not have to be either entirely accident-related or entirely pre-existing. Both factors may contribute to the claimant’s presentation.
The accident may have caused an initial injury, aggravated an underlying condition temporarily and then ceased to be the main explanation for continuing symptoms. It may also have permanently worsened one aspect while leaving other symptoms unaffected.
The expert should explain these distinctions rather than forcing the evidence into a single conclusion. Where a precise division cannot be made, the report should say so and provide the clearest clinically supportable assessment.
If the claimant’s account of being symptom-free is accepted, one conclusion may follow. If the records show ongoing symptoms before the accident, the attributable period may be shorter.
Prognosis Must Reflect the Underlying Condition.
A claimant with a pre-existing condition may recover more slowly, but the entire long-term prognosis should not automatically be attributed to the accident. The prognosis should identify the likely recovery from the aggravation and the future course of the underlying condition. It should explain whether the claimant will return to the pre-accident baseline, retain additional symptoms or develop problems that would have occurred regardless of the accident.
Treatment recommendations should distinguish between treatment required because of the accident and treatment that would have been needed in any event.
The Expert Must Explain the Difference.
The central question is not simply whether the claimant had a condition before the accident. It is whether the accident made a measurable difference to the symptoms, function or timing of that condition.
A strong report identifies the pre-accident baseline, explains the worsening, considers the condition’s natural history and gives a reasoned opinion on duration and prognosis. It avoids assuming that a pre-existing abnormality defeats causation, while also avoiding attribution of every later symptom to the accident.
Where an accident aggravates rather than causes a condition, the expert’s task is to isolate the additional harm as fairly as the medical evidence allows. That provides a more accurate account of what the accident actually changed.
