The severity of a back sprain can range from mild to severe. Sudden movements can cause injury to the ligaments because the muscles don't have time to react as would happen in a fall or car accident. The muscles don't contract enough to keep the spine within its normal range of motion, causing ligaments to stretch, bruse or tear. Moderate [tag]back sprains[/tag] cause moderate back pain and swelling with bruising. Minor back sprains (slight tearing or overstretching of a ligament) cause minor back pain and swelling with little or no bruising.
More on Back Sprains Caused by an Accident or Fall Can Be Serious

More on Back Sprains Caused by an Accident or Fall Can Be Serious