Muscle strains and lumbar sprains are the most common causes of low back pain. A low back muscle strain occurs when the muscle fibers are abnormally stretched or torn. A lumbar sprain occurs when the ligaments, the tough bands of tissue that hold bones together, are torn from their attachments. Differentiating a strain from a sprain can be difficult, as both injuries will show similar symptoms. Many doctors refer to both injuries as a category called “musculoligamentous injuries” of the lumbar spine. In general, it doesn’t matter what you call the problem because the treatment and prognosis for both back strains and sprains is the same.