HurtCallMax · Alberta injury resources
A pre-existing condition does not automatically eliminate an injury claim. It can make the evidence about your condition before and after an incident particularly important.
Two different ideas
In Athey v. Leonati, the Supreme Court of Canada distinguishes taking an injured person as they are from compensating for deterioration that would have happened anyway. The thin-skull principle addresses unusual vulnerability; the crumbling-skull discussion addresses loss attributable to a pre-existing condition rather than the defendant’s conduct.
Those labels do not decide your case on their own. Causation and the evidence about the person’s original position still matter. A lawyer needs the facts and relevant medical evidence rather than an online checklist that assigns a percentage reduction.
Build a before-and-after picture
- Earlier symptoms, treatment and any periods of improvement.
- Work, recreation and daily activities before the incident.
- What changed afterward and when the change was first recorded.
- Medical recommendations, restrictions and relevant records from both periods.
Be candid about the history
Do not conceal earlier injuries or assume every symptom has the same cause. Give your lawyer the full history so they can identify what evidence supports a change and what may need expert assessment. An incomplete history can make a sound assessment harder.
Questions for your lawyer
Ask which part of the claimed loss is disputed, what evidence would help distinguish old from new effects and whether an expert opinion is needed. There is no standard deduction simply because a person had arthritis, prior pain or a previous collision.
Why a diagnosis is not a percentage deduction
Athey did not reduce the award simply because the claimant had earlier back problems. The Court found no established measurable risk that the same herniation would have occurred without the accidents. The distinction is between a background vulnerability and a loss the person would have experienced anyway—not a rule that everyone with prior symptoms loses a fixed share.
A period without symptoms may be useful evidence, but it is not a legal certificate of full recovery. Equally, an earlier prescription or appointment is not automatic proof that all later symptoms would have happened regardless. Give the lawyer a complete chronology so those questions can be examined.
A practical before-and-after comparison
- List the earlier condition, relevant providers and the approximate treatment dates, identifying dates that need confirmation.
- Describe what you could do before the incident: the actual job tasks, household work, driving and recreation.
- Record any restrictions already in place instead of attributing every limitation to the new event.
- Describe the change after the incident and when another person or a professional first recorded it.
- Include improvements and setbacks. A changing condition should not be forced into an all-or-nothing account.
- Identify later incidents or other possible causes so that the lawyer can assess them openly.
Medical evidence and authorizations
Ask the lawyer which records would help distinguish the baseline from the change and whether an expert opinion is needed. A treating record may describe a symptom without answering its cause; an imaging finding may require interpretation rather than an assumption about when it became significant.
Discuss the scope of requested medical information before signing an authorization you do not understand. There is no standard two-year or ten-year lookback that resolves every case. Preserve the records and let the legal and medical questions determine relevance.
Avoid building a claim around a label
Do not ask a treating professional to adopt a legal slogan or a history that is inaccurate. Explain your actual symptoms, earlier condition and change in function. The question is what the evidence supports, not which label sounds most favourable.
Causation, the nature of the injury and the assessment of loss can raise separate issues. This guide explains the distinction and the information to organize; it does not provide a complete causation test for every kind of injury case.