The baseline is the starting point.
Every proper causation analysis begins before the accident. The question is not simply whether a pre-existing condition existed, but what it was doing immediately before the index event. Was the condition active or dormant? Was it stable or deteriorating? Was the claimant receiving treatment, taking medication or experiencing restrictions? Were they working, driving, exercising and managing daily tasks normally? Were there previous accidents or flare-ups?
A diagnosis alone tells us little. Degenerative changes may exist without causing symptoms, and previous episodes of pain may have resolved. A claimant may have a psychiatric history but have been functioning well, and without a clear pre-accident baseline, the opinion risks becoming speculation.
Degeneration is different from disability.
Imaging may identify cervical spondylosis, lumbar disc degeneration, osteoarthritis or other age-related changes. Those findings do not determine causation by themselves. Degeneration is common and may be symptomatic or asymptomatic. It may explain some symptoms, increase vulnerability to injury or indicate that symptoms might have developed later without the accident. However, age-related change is not the same as inevitable disability.
A scan must therefore be considered alongside the clinical history, examination findings, chronology and medical records. A claimant with previously asymptomatic degeneration may still have suffered an accident-related aggravation. A claimant with active symptoms before the accident may have a more limited accident-related claim.
Aggravation, acceleration and natural progression.
The language used must be precise. An accident may cause a new injury, aggravate an existing condition, accelerate symptoms that would otherwise have appeared later, or cause a temporary flare-up. Alternatively, it may make no material difference to the long-term position. These conclusions are not interchangeable. Aggravation generally means that the accident worsened an existing condition however, acceleration means that symptoms or disability were brought forward. Natural progression means that deterioration would have occurred regardless of the accident.
For example: increased back pain lasting six months before a return to baseline may support temporary aggravation, whilst degenerative knee disease requiring surgery earlier than expected may raise acceleration. A claimant already deteriorating rapidly before an accident, with no clear change afterwards, may be experiencing natural progression. The distinction affects valuation. A permanent new injury is different from a temporary worsening, and a two-year acceleration is different from lifelong accident-related disability. The expert should identify what changed and for how long.
Medication and records reveal the pattern.
Medication history can provide a useful objective chronology. It may show whether symptoms were treated before the accident and whether pain relief, anti-inflammatory medication, antidepressants, sleeping tablets or neuropathic medication were introduced or increased afterwards.
No relevant medication before the accident followed by repeated prescriptions may support deterioration. Similar prescriptions before and after the accident may require the expert to explain what materially changed. A claim of severe symptoms without corresponding treatment may also require explanation. Medication is not decisive. A prescription does not prove that it was taken, and some claimants use over the counter or private treatment. Nevertheless, it can help distinguish reported change from documented change.
Medical records may support both sides. They may record earlier symptoms but also demonstrate a clear post-accident deterioration. Selective review is therefore dangerous. Claimants cannot ignore inconvenient entries, while defendants cannot treat every historic reference to pain as fatal. Records created close to the accident are often especially important. Did the claimant report new or worsened symptoms? Were accounts consistent? Did medication, treatment, work absence or referrals change? Causation is usually built through chronology, not isolated entries.
Function decides more than diagnosis.
In pre-existing condition disputes, function is often more informative than the diagnostic label. Two claimants may have similar imaging findings but very different levels of disability.
The expert should examine whether the claimant’s ability to work, complete domestic tasks, sleep, drive, exercise or socialise changed after the accident. Did mobility reduce? Did care needs arise? Was the change supported by records or witness evidence? A diagnosis explains the medical background. Function explains the loss. A clear functional deterioration may support an accident-related claim despite a pre-existing condition. Where function did not materially change, the claim may be harder to justify.
Avoid all-or-nothing conclusions.
The medical answer often lies between the parties’ positions. The accident may have caused a temporary worsening, brought symptoms forward or increased treatment needs for a defined period without explaining the claimant’s entire presentation. That is not fence-sitting, it is often the correct analysis.
The expert should apportion cause, time or effect where the evidence permits and acknowledge uncertainty where it does not. If records are incomplete, imaging cannot distinguish old change from new symptoms, or the claimant’s account conflicts with contemporaneous evidence, the report should say so.
The report must answer the real question.
The central issue is not whether a pre-existing condition existed, but whether the accident made a material difference. That difference may involve new symptoms, increased severity, reduced function, additional treatment, earlier deterioration or a worse prognosis.
A good report clearly explains the pre-accident baseline, the post-accident changes and the natural course. It does not treat vulnerability as a defence or attribute every later symptom to the accident.
The sharper questions are: What was present before the accident? What changed afterwards? What would have happened anyway?
That is where causation is won or lost.
