The problem for sufferers of occupational overuse syndrome is that from both a medical and legal perspective, it is difficult to differentiate between psychological and physiological pain. Pain is a subjective issue. At one end of occupational overuse syndrome, there will be clear evidence of a sprain or strain involved with carpal tunnel syndrome. At the other end, there will be no or inconclusive evidence of physical pain for fibromyalgia or non-specific arm pain (‘NSAP’) where no actual physical injury can be identified.
There must be a causal connection between a specified event or specified events that caused a physical injury, for example, a strain or sprain. The definition of personal injury in section 26(1)(b) of the Accident Compensation Act 2001 (‘ACA 2001’) does not include pain, which is seen as psychological rather than physiological in nature.
Whether pain alone should constitute a physical injury has divided commentators. The question has been considered by the Supreme Court decision in Allenby v H  NZSC 33 where a pregnancy as a result of a failed sterilisation was held to be a physical injury due to the profound impact on the physiology of a woman.
However, the law about whether occupational overuse syndrome is covered by the ACA 2001 is settled. There needs to be a physical injury. In a recent case before the High Court which has since been discontinued, Paula Cone v ACC and Fonterra Cooperative Group Ltd  NZACC 3 (DC);  NZACC 265 (DC), Ms Cone tried to extend the boundaries of ‘physical injury’ to include NSAP, arguing that NSAP is a qualifying injury to receive accident compensation under ACA 2001.
By way of background, ACC had rejected cover for Ms Cone. They said her NSAP was not a consequence of any physical injury within the meaning of ACA 2001. There was no evidence of physical damage to her body. Swelling was held not to be an indication of a physical injury. The District Court also dismissed her claim. It rejected Ms Cone’s argument that there was a ‘general proposition that where there is pain it is likely that there has been a physical injury’. The High Court also dismissed her application for leave to appeal to the High Court. Ms Cone then applied for special leave to appeal to the High Court but subsequently discontinued the proceedings.
With the Health and Safety at Work Act 2015, employers must provide a safe working environment including having systems in place to eliminate wherever possible occupational overuse syndrome. It is a known medical condition whether or not it qualifies for ACC. Failure to have good systems in place, including worker participation in how to eliminate, minimise and manage this problem could not only draw the attention of WorkSafe where harm to workers results from non-compliance but there is also the possibility in certain circumstances of exposure to a new type of personal grievance under section 103(1)(j) of the Employment Relations Act 2000 which prevents employers from engaging in adverse conduct for a prohibited health and safety reason or coercing / inducing an employee to perform a harmful function.