Answer:
As the name implies, it is a pathology secondary to a repetitive action such as typing, knitting, doing a job task, etc. Basically, you overuse some part of your body to the point where it causes a problem. The best way to prevent a RSI is to avoid doing what is causing the problem. To help you may also build strength in the effected area and/or do some self-maintenance such as stretching, icing and resting. Often, people with a RSI try to overcome their situation without avoiding the action(s) that caused the problem and become worse. A RSI usually gets better and worse with the worse becoming more predominant over time and interfering with the person's ability to continue said activity and interfering with their usual daily routine.