Acute low-back pain without sciatica, with some spread of discomfort to the region of the sacroiliac joint, to the outer part of the buttock as well as to the lateral and the back part of the thigh, is a unifying symptom of a very common clinical syndrome whose exact underlying cause remains often uncertain. Most patients fall then into the category of nonspecific low-back pain. Probably the pathogenesis is not uniform, and the pain can arise from a variety of structures (muscles, ligament, spine). Pain which persists after 3 to 4 days should warn the clinician that a serious pathological condition may be present which requires a new approach to diagnosis and treatment.