The back is a highly complex part of the body as it contains joints, nerves, muscles, and bones. Because of this, the most common causes of back pain can be very hard to determine, as there are so many parts that it could affect. In the majority of cases, the issue is not really serious and not related to a disease. Rather, most people have an irritated or pinched nerve, an injury or strain, or a minor sprain. This is often caused by general day to day activities, but they can become worse over time.