We have all heard of carpal tunnel syndrome. That is a tightening of the muscles around the nerves in a person's wrist. Once the muscles tighten due to extended repetitive motion such as production work, then that could be considered a job injury.
There are many other situations like this with regard to someone's low back or elbow or neck. However, people tend to think that unless they have a specific one-time incident of lifting or falling or twisting, then their injury will not be considered a job injury. That is wrong. Job injuries occur whenever a person's need for medical treatment is the result of their job duties. There are many people who fail to report this type of injury or who believe they have not had a job injury or they just don't want to get into a fight over whether they have actually had a job injury.
If this injury is disabling, (meaning you cannot work full-time or you cannot work at all) then you should pursue a claim for a job injury because it will not get better unless it is treated.
I can give you a number of examples where people come to me, asking me if a job injury could occur when they perform certain functions, and I say that as long as a doctor can causally connect the injury to the job duties performed then you have a job injury and we can pursue a claim.
This is not to say that the insurance company will not try to fight it. Insurance companies LOVE to try to fight these cases in order to discourage people from receiving benefits or talking to your coworkers if this happens to them.
Remember, workers' compensation is a war, and the insurance companies and your employer will treat it as such. Many of my clients are much too idealistic and seem to care more about their employer than their employer cares about them. The best thing to do when dealing with these types of situations is to call a lawyer and discuss it with him or her with confidentiality in the lawyer's office.