Practical review
What to check in this situation
- Build a before-and-after chronology of symptoms, function, duties, treatment and imaging.
- Ask the medical expert to address the actual work mechanism and competing non-work explanations.
- Keep liability separate from any later section 323 deduction for pre-existing permanent impairment.
Records that may help
Keep earlier and current clinical records, pre-injury function evidence, task records, imaging chronology, treatment response and the insurer or IME report.
Next procedural step
Answer the insurer's exact causation proposition and seek advice where the wrong injury classification or WPI deduction is being used.
Overview
A pre-existing condition does not automatically defeat a NSW workers compensation claim. The first question is what injury is alleged. A discrete personal injury and the aggravation of a disease are governed by different statutory causation tests.
Identify the legal test before answering the denial
- • For a personal injury other than a disease injury, section 9A generally asks whether employment was a substantial contributing factor.
- • For a disease or disease aggravation, section 4 generally asks whether employment was the main contributing factor.
- • A before-and-after change can be important evidence, but it does not replace the correct statutory test.
- • ILARS funding may be available for an eligible dispute if an approved lawyer obtains a grant; it is not automatic.
What the law actually says
Section 4 of the Workers Compensation Act 1987 distinguishes a personal injury from a disease injury. For a personal injury other than a disease injury, section 9A generally requires employment to be a substantial contributing factor. A disease contracted in the course of employment, or the aggravation, acceleration, exacerbation or deterioration of a disease, generally requires employment to be the main contributing factor.
The diagnosis and facts determine which test applies. Evidence that a worker performed ordinary duties before a particular event or period of exposure, then developed new restrictions or incapacity, may help. It does not by itself establish whether employment was the substantial or main contributing factor.
Liability and a later WPI deduction are different questions
Sections 4 and 9A address whether the alleged work injury is compensable. Section 323 of the 1998 Act addresses a later permanent impairment assessment and requires a deduction only for the proportion of impairment due to a previous injury, pre-existing condition or abnormality.
In Walton v State of New South Wales (Hunter New England Local Health District) [2026] NSWSC 824, the Supreme Court confirmed that an earlier condition must first be shown to contribute to the assessed degree of permanent impairment. Earlier pain, degeneration or a diagnosis does not alone establish the deduction. Read the Walton section 323 case note.
Illustrative example
A store worker had intermittent back stiffness and an older scan showing degeneration but was performing normal duties without restrictions. After repeatedly unloading unusually heavy stock over several weeks, the worker developed persistent leg symptoms, reduced capacity and new treatment needs. The claim would require a medical diagnosis and analysis of whether the facts amount to a personal injury or an aggravation of disease, followed by the correct substantial- or main-contributing-factor test. The earlier scan is relevant, but it neither proves nor defeats liability by itself. This example does not predict the claim outcome or any WPI deduction.
How insurers usually frame the denial
- Degeneration argument: the insurer relies on wear-and-tear findings on MRI or CT as an alternative explanation.
- Old records argument: they search GP notes for any prior pain complaint, even if you had kept working without restriction.
- Natural progression argument: they say your symptoms would have happened anyway, regardless of work.
- IME argument: the insurer relies on an independent medical opinion that differs from the treating evidence.
When that happens, it helps to compare the denial against the broader guides onunfair IME reports,section 78 notices, anddenied claims generally.
How to challenge the denial properly
A useful response addresses the insurer's actual statutory and medical reasoning. A before-and-after history can support that response, but the evidence should also identify the diagnosis and explain whether employment met the substantial-contributing-factor or main-contributing-factor test that applies to it.
Keep the section 78 notice and its date of receipt. The time and procedure for an insurer review, PIC dispute, medical appeal or another entitlement depend on the decision and claim circumstances. Asking a case manager to reconsider the file does not necessarily preserve every formal period, so obtain advice promptly where payments, treatment or liability have been disputed.
Establish the baseline
Show you were working before the incident, doing normal duties, and not suffering the same level of restriction or incapacity.
Prove the change
Use certificates, specialist evidence, imaging context, and witness material to show a fresh worsening, new symptoms, or materially increased incapacity after work exposure.
Answer the insurer doctor
Where an IME attributes the condition to natural degeneration, ask whether the treating or independent medical opinion identifies the diagnosis, addresses the competing causes and applies the correct statutory test for that injury.
What can go wrong before a pre-existing-condition dispute is properly documented
The scan gets treated like the whole case
MRI and CT reports often mention degeneration, disc bulges, arthritis, or age-related changes. Insurers then rely on those words as the alternative cause. Imaging does not answer the statutory question by itself. The diagnosis, clinical history, function, work exposure and competing causes must be considered together.
No one captures the worker's baseline properly
Many workers had old pain, old imaging, or even prior treatment but were still doing full duties before the work event. If that baseline is not written down clearly, the insurer can collapse the whole timeline into "this was always there".
The insurer doctor reframes aggravation as natural progression
A short insurer exam can be used to support aone-sided IME report, then hardened into aSection 78 denial. If treating doctors do not answer that reframing quickly, the file drifts toward a formal dispute.
Income and treatment issues start compounding
Once the insurer says the condition is pre-existing, it often starts affectingweekly payments, surgery approvals, and rehabilitation planning at the same time. The dispute stops being academic very quickly.
Evidence that often changes these cases
- Treating GP and specialist notes showing your function before and after the work event.
- Certificates of capacity that explain exactly which duties became impossible.
- Employment evidence describing lifting, repetition, awkward postures, pace, or the traumatic event itself.
- Old imaging interpreted in context, especially where degenerative findings existed without serious symptoms before work.
- Statements from supervisors, co-workers, family, or rehabilitation providers about the sudden functional change.
If the denial has also affected your income or treatment approvals, look at the connected guides onstopped weekly payments,treatment denials, andthe PIC dispute process.
Best next guide by insurer argument
If your denial letter leans heavily on one argument, go straight to the matching guide and build evidence in that sequence.
- "It is degeneration / pre-existing only" → stay on this page and build your before-and-after functional evidence first.
- "Our IME says no work causation" → review the unfair IME report guide and respond point-by-point.
- "Section 78 liability denied" → use the Section 78 notice guide for timeline and document order.
- "Weekly payments reduced or stopped" → triage with the weekly payments stopped guide in parallel.
Frequently asked questions
Do I have to disclose my old injuries in a workers comp claim?
Give a complete and accurate history when the insurer, treating practitioner or assessor asks for it. Earlier symptoms do not decide the claim by themselves, but incomplete answers can create a credibility dispute and make it harder to explain what changed at work.
What if I had surgery on the same area before my work injury?
Prior surgery does not automatically defeat a later claim. The medical diagnosis and facts determine whether the alleged work injury is a new personal injury or a disease aggravation, and the applicable statutory causation test must still be proved.
Which causation test applies when there is a pre-existing condition?
For an injury other than a disease injury, section 9A generally requires employment to be a substantial contributing factor. For a disease, or the aggravation, acceleration, exacerbation or deterioration of a disease, section 4 generally requires employment to be the main contributing factor. The diagnosis and legal classification therefore matter.
Should I deal with liability, treatment, and weekly payments separately if the insurer says it is only a pre-existing condition?
The issues can share the same medical history, but each decision still has its own statutory question. Keep one accurate chronology and all decision letters, then identify separately what the insurer decided about liability, weekly payments, treatment and permanent impairment.
Does a pre-existing condition automatically reduce my WPI?
No. Section 323 concerns the proportion of permanent impairment due to a previous injury, pre-existing condition or abnormality. The NSW Supreme Court confirmed in Walton that the earlier condition must contribute to the assessed degree of permanent impairment before a deduction is made. This is a different question from whether the work injury is compensable.
This guide is general information about NSW workers compensation and is not a substitute for legal advice about your own claim, medical evidence, or time limits.
Related dispute and evidence guides
- Workers compensation services (NSW)
- Resources hub
- Disputes hub
- Section 78 notice guide
- Claim denied guide
- Unfair IME report guide
- Surgery denied guide
- Treatment denied guide
- Occupational disease and work-related aggravation guide
- Walton section 323 pre-existing-condition case note
- Weekly payments stopped guide
- PIC dispute process
- Start free claim check
Get the injury classification and evidence reviewed
If the insurer says your symptoms are just degeneration or a pre-existing disease, get the denial reviewed before more benefits are lost.
Last reviewed: 21 July 2026. This page is general information and is not legal advice.