Most Common Causes of Low Back Pain are:

Strains- Muscles of the low back can rip or tear. A strain is a result of a heavy load or sudden force applied to the muscles before they are ready for activity. The muscle essentially rips, along with blood vessels with in the muscle tissue. This may cause bleeding into the injured area (inflamation). It can take up to 2 to 3 hours before sufficient bleeding or irritation sets in to produce significant pain. This can help to explain why many people often can tolerate finishing the task at hand, only to suffer from intense pain later. This tear in the muscle tissue is followed by symptoms such as: Pain, swelling, and muscle spasms.

Sprains- refer to an overstretching of one or more of the ligaments of the back. The ligaments can be stretched beyond their natural integrity and in some cases can completely tear. It is common to have both ligament sprains and muscle strains occuring together. This is especially the case in severe falls and motor vehicle accidents.