Microtrauma injury: when there is no single event to point to
The microtrauma doctrine recognises damage caused by many repeated minor injuries rather than by a single event. The National Insurance Institute sets three cumulative conditions, and the decisive one is in fact the factual foundation of the repeated movement.
What microtrauma is
Work injury law is usually built around an event: something happened, on a particular day, and caused harm. The microtrauma doctrine deals with a different situation - damage caused by many minor injuries, repeated over and over.
The National Insurance Institute describes the distinction with a familiar image: not a rushing stream, but drops falling on a stone and eroding it over time. Each movement on its own is harmless, but their accumulation causes real damage.
This is a third route, alongside a work accident and an occupational disease, and it is relevant precisely in the cases that fall into neither of those.
Source: National Insurance Institute, circular on the microtrauma doctrine.
The three conditions
The Institute circular sets out three cumulative conditions:
- A factual foundation - proof that repeated movements were performed.
- Medical foundation - a physician determination that the accumulated minor injuries caused real, irreversible damage.
- Causal connection - a connection between those movements and the working conditions.
All three are required together. The absence of one defeats the claim, even where the other two are well established.
Source: National Insurance Institute, microtrauma circular.
Which movements count
Not every repetitive job gives rise to a cause of action. The circular sets out the characteristics required of the movements:
- That they are identical or substantially similar to one another.
- That they are focused on a defined location in the body.
- That they were performed at sufficient frequency and over sufficient periods of time.
The circular also makes clear that absolute continuity is not required: the movements may form part of concentrated work sequences, and need not be a single unbroken activity.
The distinction matters in practice, because most jobs are not entirely monotonous, and the question is whether there is a core of repeated movement directed at the same part of the body.
Source: National Insurance Institute, microtrauma circular.
Microtrauma against occupational disease and accident
The three routes differ in what they require:
- A work accident requires a sudden event that can be described.
- An occupational disease requires the disease to appear on a closed list in the regulations, and the exposure conditions the list sets to have been met.
- Microtrauma requires neither an event nor a listing, but proof of the repeated movements and of their connection to the damage.
Hence the practical value of this route: it answers situations in which the work caused real damage, but there is no single event to point to and the condition is not on the list.
Source: National Insurance Institute, microtrauma circular.
What establishes such a claim
The first element, the factual foundation, is usually what decides the matter. It is built from material that is not medical:
- A precise account of the repeated action - what exactly was done, in what posture, how many times per shift.
- The length of the period during which the work was performed in that way.
- Documentation of the workplace: roles, equipment, procedures, and at times the evidence of colleagues.
The second element rests on a medical opinion connecting the pattern of movement to the finding, not merely confirming that a finding exists.
In practice, a gap between the description of the work as recorded in the claim and the description given later is one of the common reasons for rejection. Precision at the first stage therefore matters more than later supplements.
In summary
The microtrauma doctrine recognises damage caused by the accumulation of repeated minor injuries rather than by a single event. The National Insurance Institute sets three cumulative conditions: a factual foundation of repeated movements, medical foundation of irreversible damage, and a causal connection to the working conditions. The movements must be identical or substantially similar, focused on a defined location in the body, and performed at sufficient frequency and over sufficient time.
This is the route that answers cases where there is no event to point to and the condition is not on the register of occupational diseases. What decides it is the quality of the factual account of the work, not the medical finding alone.
If your work involves a repeated action and you are suffering an injury to that same part of the body, contact us with a description of the work and the medical material. We will consider whether the route fits and what the first step is.
The questions that come up most
What is required for a microtrauma injury to be recognised?
Which movements count?
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What usually decides such a case?
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Tell us exactly what you do at work, how often and for how long, and what the medical findings are. We will consider whether the route fits.