Acute or short-term low back pain generally lasts from a few days to a few weeks. Most acute back pain is mechanical in nature — that is musculoskeletal low back pain. Musculoskeletal low back pain can be caused by problems with the alignment in your vertebrae, pelvis, or sacroiliac joint (where your spine meets your pelvis), tightening or shortening of muscles in the area, lack of or too much mobility in your spine or a specific syndrome termed “myofascial pain syndrome”. Myofascial pain is pain arising from active trigger points in a muscle or its fascia (connective tissue around the muscle). A trigger point is a tender, irritated area that can cause pain in areas along the muscle; an event called “referred pain.” This referred pain can usually be reproduced when the trigger point is “palpated,” or pushed on. The pain can be felt at rest, as well as when the muscle is being used. Trigger points over time cause the muscle to shorten, leading to a tight, pulling, or stretched feeling.