Causation asks whether the incident produced the condition. Apportionment asks how much of the resulting impairment belongs to the incident and how much to what came before. Nearly every independent medical examination referral asks for both, and both are opinions, which means the examiner will be asked to defend the reasoning behind them. The failures are the same in either direction: an opinion stated with more certainty than the record supports, or one stated so vaguely it decides nothing. The method below keeps the opinion within what the evidence supports.
In most United States forums the standard for a medical-legal opinion is reasonable medical probability: more likely than not. Some jurisdictions use the phrase reasonable medical certainty, which courts generally treat as the same threshold, and some workers' compensation systems define their own. Confirm the language the retaining party needs and use it, exactly and consistently. An opinion offered as "possible" does not meet the standard and will be treated as no opinion. An opinion offered as "certain" invites the question of how the examiner can be certain from a record, and the honest answer weakens everything else.
The reasoning most examiners use, whether or not they name it, runs through a short set of questions, each answered from the record.
Did the condition exist before the incident? The pre-incident record answers this: primary care notes, prior imaging, pharmacy history, prior claims. Absence of prior complaints in a thin pre-incident record is weak evidence; absence in a thorough one is strong.
Is the mechanism capable of producing the condition? A rear-end collision at low speed and a cervical strain are consistent. The same collision and a rotator cuff tear need a mechanism in the record, such as a braced arm on the wheel, and the examiner should say whether one is documented.
Did symptoms follow the incident in a plausible time course? The first documented complaint of the region is the fact here, and its date relative to the incident. A complaint recorded at the emergency department the same night is one fact; a complaint first recorded at week nine, after seven visits where the region was not mentioned, is another, and the report has to reckon with it rather than skip it.
Do the objective findings fit? Imaging, examination findings, and operative findings either support the diagnosis attributed to the incident or they do not, and where a finding is described in terms suggesting chronicity, the report should say so.
Are there other explanations? A second incident, a physically demanding occupation, a documented prior episode, a degenerative process. The report should name the alternatives the record raises and say why the examiner does or does not find them more likely.
The opinion is then the conclusion of that reasoning, stated once, to the standard: it is my opinion, to a reasonable degree of medical probability, that the collision of March 12 caused a cervical strain that resolved by the discharge from physical therapy on June 3, and did not cause the C5-6 disc protrusion, which is more likely than not degenerative in origin for the reasons above.
Many referrals turn on a pre-existing condition that was made worse. The usual distinction in compensation practice is between an exacerbation, a temporary worsening that returns to the prior baseline, and an aggravation, a permanent worsening of the underlying condition. The terms are not used identically in every jurisdiction, so define what you mean when you use them. Either way the opinion depends on establishing the baseline from the pre-incident record: what the person's symptoms, function, treatment, and work status were before, from documents rather than recollection. A report that asserts a baseline without citing where it came from has no baseline.
Where an impairment rating is requested and part of the impairment predates the incident, most systems ask the examiner to divide it. Rules differ substantially: some jurisdictions apportion only to a previously rated or documented impairment, some to any pre-existing condition that contributes, some prohibit apportionment to asymptomatic conditions. Ask the retaining party which rule applies, and follow the edition of the AMA Guides or the state schedule the forum requires. Within those rules, the reasoning should be visible: the total impairment, the evidence of pre-existing impairment and its magnitude, the share attributed to each, and the basis for the division. An apportionment stated as a bare percentage with no reasoning is an invitation to ask how the number was chosen, and "clinical judgment" is not an answer that survives the follow-up.
Every causation opinion rests on a record that could be incomplete, and the strongest reports say so specifically. "No imaging of the lumbar spine prior to the incident is in the record; a prior study, if one exists, could change this opinion." "The physical therapy records for April through June were not provided." Naming the gap does two things: it shows the examiner reviewed the record carefully enough to know what was missing, and it takes away the deposition question of whether the examiner would have wanted to see it.
It is not a legal conclusion. Proximate cause, compensability, and liability are for the tribunal, and an examiner who uses those words is asked to define them. It is not a credibility finding; discrepancies between the claimant's account and the record are facts to document, not character to characterize. And it is not an answer to a question that was not asked. Answer the referral questions, in order, to the standard, with the reasoning and the limits, and stop.
That the conclusion is more likely than not. It is the threshold most United States courts and compensation systems require for a medical opinion to be considered. Some forums use 'reasonable medical certainty' for the same threshold. Use the phrase the retaining party specifies.
In common compensation usage, an exacerbation is a temporary worsening of a pre-existing condition that returns to baseline, and an aggravation is a permanent worsening. Definitions vary by jurisdiction, so state what you mean when you use either term.
Follow the rule the jurisdiction applies, use the required edition of the AMA Guides or state schedule, and show the reasoning: the total impairment, the evidence of pre-existing impairment, and the basis for the division. A bare percentage without reasoning is the weakest form.
Yes. Naming the missing prior imaging or therapy records, and stating that the opinion is subject to revision if they are produced, demonstrates a careful review and removes a standard deposition question.
Every page of the production read and cited, so the causation reasoning rests on all of it.
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