Hi Dave

Your question is essentially one of asking "Was this an injury that was work-related?"

I am going to suggest two ways of dealing with this:

1. You could rely on the HSE guidance instead of what RIDDOR actually says and conclude that this is akin to a "twinge".

2. You ask for medical advice - identify the task and its elements and ask whether it was reasonably foreseeable that the task might result in the symptoms described. If the answer to that question is YES, then perhaps sensible to report (assuming that the incident meets one of the RIDDOR reporting thesholds) on the basis of "if in doubt, report".

Remember that a RIDDOR is in no way an admission that there was anything wrong in how the work was being done.

RIDDOR is essentially an administrative mechanism to give HSE (and others - e.g. when the UK was in EU, a duty of the UK to inform Eurostat of accident numbers etc) intelligence as to how accidents happen and an estimate of how often.

Going down route 2 is more costly but more likely to instil confidence that you care about the workforce.