ACC and Pre-Existing Conditions in NZ (2026): When a Gradual or Degenerative Problem Isn't Covered

ACC covers injury by accident, not conditions that build up gradually. Here is how ACC decides injury versus gradual process, why degenerative and age-related problems are usually declined, and how income protection fills the gap.

ACC is built around one idea: a personal injury caused by an accident. That works well for a fall, a sports injury or a crash. It works far less well for the slow-build problems that stop people working just as often, the worn knee, the degenerating disc, the shoulder that gave out over years rather than in one moment. These are often treated as gradual or degenerative, and gradual or degenerative conditions sit largely outside ACC.

This guide explains how ACC draws the line between an injury and a gradual process, why age-related and pre-existing problems are commonly declined, the narrow work-related exception, and what private cover does when ACC says no.

TL;DR: ACC generally does not cover conditions that develop gradually, including degenerative and age-related ones, unless they meet the work-related gradual-process test under section 30(2) of the Accident Compensation Act 2001 ¹². Pre-existing conditions made worse by work are expressly excluded ³. Where ACC declines, income protection can cover income lost to illness and gradual conditions, subject to policy terms ¹⁰.

The core distinction is sudden versus gradual. ACC is designed for a discrete accident at a point in time. A problem that built up over months or years usually falls outside cover unless a specific work-related test is met ¹.

How does ACC decide if a condition is an injury or a gradual process?

ACC starts by asking whether your problem was caused by an accident, a specific external event at an identifiable point in time, or whether it developed gradually.

If a condition, disease or infection is caused gradually, ACC generally does not cover it. That includes degenerative and age-related conditions ¹. A torn ligament from a single fall is an accident. A disc that has degenerated over a decade is, in ACC's framework, a gradual process, and gradual processes are only covered when they meet a separate work-related test ¹².

This distinction matters because the same body part can be either. A sudden lifting injury that ruptures a tendon may be covered; the same tendon failing through long-term wear may not be. ACC, and sometimes its assessors, will look at imaging, history and how the problem actually arose.

The decision flow below sets out the branches in simplified form.

Figure: Sudden injury vs gradual process, ACC cover

Source: ACC rules, illustrative ¹²³.

Why are degenerative and age-related conditions often declined?

Because ACC is accident cover, not health cover. Its statutory job is personal injury by accident, not the natural progression of the body over time.

Degenerative changes, such as osteoarthritis, disc degeneration and ordinary wear-and-tear, are treated as conditions that develop gradually rather than as accidents. As a result they are generally not covered, and the position is the same for age-related conditions ¹. The label can feel harsh, particularly when a single event, bending to lift a box, seemed to "cause" the pain. ACC's question is whether the event caused a fresh injury or merely brought an existing degenerative condition to the surface.

This is also why two people with similar symptoms can get different outcomes. A younger person with no prior history and clear accident imaging may be covered, while an older person whose scans show long-standing degeneration may be declined for the same back pain, because the underlying cause is assessed differently.

What is the gradual-process work injury exception?

There is one main route to cover for a gradually caused condition: the work-related gradual process, disease or infection (WRGPDI) test. It is narrow and specific.

Under section 30(2) of the Accident Compensation Act 2001, a work-related gradual process injury must meet a three-part test ²:

1. A particular property or characteristic of the work tasks or work environment caused or contributed to the injury.

2. That property or characteristic is not found, to any material extent, in the person's non-work life.

3. The risk of suffering the harm is significantly greater for people doing that work than for people who do not.

All three parts must be satisfied. ACC may need extra assessments to decide whether a gradual-process injury qualifies, and it is explicit that some gradual-process claims cannot be covered, including pre-existing conditions made worse by a person's work environment ³.

There is a separate, easier route for certain listed occupational diseases. For Schedule 2 conditions, such as diseases caused by asbestos, lead, arsenic or mercury, you do not have to prove the three-part causation test; you only need to show the job exposed you to the relevant substance ⁴.

Outside these routes, a gradual condition is usually treated as degenerative and not covered ¹.

How do back, joint and overuse claims commonly get assessed?

These are the claims where the injury-versus-gradual line is most contested, because backs, knees, shoulders and hips all show wear over time.

When you lodge a claim, ACC looks at whether there was a clear accident, what the imaging shows, and your prior history. If scans show established degeneration, ACC may decide a recent event aggravated a pre-existing condition rather than caused a new injury, which can mean decline. Overuse and repetitive-strain problems are assessed against the work-related gradual-process test ²; if you cannot show that work had a particular characteristic meeting all three parts, the claim usually falls outside cover.

This is not ACC being awkward for its own sake. It reflects the statutory boundary between accident cover and the gradual, ordinary changes of living and ageing. The practical effect, though, is that people doing physical work for years can find the very wear that work contributed to is hard to get covered unless the three-part test is clearly met.

For a fuller view of where ACC stops as an income tool, [ACC is not income protection: five limits](acc-is-not-income-protection-five-limits-nz) walks through the related gaps.

What happens when ACC says your problem is pre-existing?

If ACC decides your problem is pre-existing, degenerative or otherwise gradual and not work-related, it declines cover. That means no weekly compensation and no funded treatment for that condition through ACC.

Where ACC cover does apply, weekly compensation pays up to 80% of pre-incapacity gross weekly earnings, before tax and other deductions ⁵, and generally starts from day 8 of incapacity, the first week is not paid by ACC, though for a work injury the employer covers that first week at 80% of the prior seven days' earnings ⁶. There is a full-time minimum, set at $752.00 gross per week from 1 April 2025, based on 80% of the adult minimum wage of $23.50 an hour over a 40-hour week ⁷.

A decline removes all of that for the condition in question. You are then reliant on sick leave, savings, any health insurance for treatment, and any income protection you hold. This is the moment many people discover the limit the hard way, having assumed ACC would step in for anything that stopped them working.

A condition that stops you working through illness rather than an accident sits in the same gap. [Off work through illness, not injury](off-work-illness-not-injury-income-cover-nz) covers that scenario in detail.

Why income protection matters when ACC declines a gradual condition

This is the practical reason the distinction matters. The conditions ACC is most likely to decline, gradual, degenerative, age-related and most illnesses, are exactly the ones income protection is designed to cover.

Income protection insurance covers loss of income from illness and from conditions ACC will not cover, including most gradual, degenerative or age-related conditions, subject to the policy terms and the product disclosure statement ¹⁰. Cover can be compared across major New Zealand insurers, including Partners Life, AIA, Asteron Life, Fidelity Life and Chubb, on definitions, wait periods and price. Whether a claim is paid depends on the specific policy, your disclosure and any exclusions, so the wording matters.

The point is not that income protection is "better" than ACC; the two do different jobs. ACC handles accidents, no-fault and automatically. Income protection is built to respond to the broad category of illness and gradual conditions that ACC was never meant to cover. Held together, they close most of the gap.

Cover under any policy is subject to its terms, exclusions, stand-down periods, underwriting and your disclosure ¹⁰.

Can you challenge an ACC cover decision?

Yes. ACC decisions are not the final word, and there is a formal process with strict timeframes.

If you disagree with an ACC cover decision, you can apply for a review using the ACC33 form. You must apply within three months of the date on your ACC decision letter; late applications are accepted only in limited or exceptional circumstances ⁸. At the review, an independent reviewer issues a binding written decision within 28 days of the hearing. If you disagree with that, you can appeal to the District Court, generally within 28 days ⁹.

Reviews often turn on medical evidence, so supporting reports from your GP or specialist can matter. Free help is available, including from Community Law and advocacy services.

How do you make sure a gap like this doesn't leave you unpaid?

The honest answer is to look at the gap before anything goes wrong, not after a decline letter arrives.

A few things people in this position often weigh up:

• Know what ACC does and does not cover. Accidents yes; gradual, degenerative and age-related conditions and most illness, generally no ¹.
• Check your sick leave and savings buffer. If ACC declines and you have no income cover, this is what you fall back on.
• Consider income protection for the illness and gradual gap. It is designed for the conditions ACC leaves out, subject to terms ¹⁰.
• Read the wording, including exclusions and stand-downs. A summary like this is not the policy; the product disclosure statement governs what is actually paid.
• If you have been declined, mind the clock. The three-month review window runs from the decision letter ⁸.

If a claim is declined and you are unsure why, [common reasons income protection claims are declined](income-protection-claims-declined-reasons-nz) is a useful companion read on how to keep cover claim-ready.

Frequently asked questions

Does ACC cover degenerative or age-related conditions in NZ? Generally no. Conditions caused gradually, including degenerative and age-related ones, are usually outside ACC unless they meet the work-related gradual-process test under section 30(2) of the Accident Compensation Act 2001 ¹².

What is the work-related gradual process test? It is a three-part test: a property or characteristic of your work caused or contributed to the injury, that characteristic is not found to any material extent outside work, and the risk is significantly greater for people doing that work than for others. All three parts must be met ².

Why would ACC call my back or knee problem pre-existing? If imaging or history shows established degeneration, ACC may decide a recent event aggravated a pre-existing condition rather than caused a new injury, which can lead to a decline. Pre-existing conditions made worse by work are also expressly excluded ³.

How do I challenge an ACC decision? Apply for a review using the ACC33 form within three months of the date on your decision letter. An independent reviewer issues a binding decision within 28 days of the hearing, and you can then appeal to the District Court, generally within 28 days ⁸⁹.

Can income protection cover what ACC declines? It can. Income protection is designed to cover income loss from illness and from gradual, degenerative or age-related conditions that ACC will not cover, subject to the policy terms, exclusions and your disclosure ¹⁰.

Does ACC pay anything while a gradual condition stops me working? Only if the condition is covered. Where ACC applies, it pays up to 80% of pre-incapacity gross weekly earnings, generally from day 8 ⁵⁶. If the condition is declined as degenerative or pre-existing, ACC pays nothing for it ¹.

This article is general information only and is not personalised financial advice. It does not take into account your particular financial situation, goals or needs. Before acting, consider whether it's right for you and seek advice tailored to your circumstances.

Smiths Financial is a trading name of Craig Smith Business Services Ltd (FSP712931), which holds a Class 2 financial advice provider licence issued by the Financial Markets Authority to provide financial advice on personal risk insurance, health insurance, general insurance, KiwiSaver and managed funds. Our advisers, Henry Smith (Financial Adviser) and Craig Smith (Principal Adviser), are bound by the Code of Professional Conduct for Financial Advice Services and the duty to give priority to clients' interests. Craig Smith Business Services Ltd is a member of the Financial Dispute Resolution Service (FDRS), a free and independent dispute resolution scheme. Whether a claim is paid depends on the terms, conditions, exclusions, stand-down periods and underwriting of the specific policy, and on your disclosure; this is a summary only, always read the policy wording. We're generally paid by commission from the insurer when you take out a policy through us; this doesn't change the premium you pay, and we manage any conflicts in line with our duty to prioritise your interests. Written by Henry Smith, Financial Adviser, reviewed by Craig Smith, Principal Adviser. Last reviewed 6 June 2026.