Radicular pain in the territory innervated by the L4-L5 nerve root, resulting from a herniated lumbar intervertebral disc, is a frequent and disabling event. Most cases resolve spontaneously. The assessment of radiating acute lumbar back pain begins by excluding serious spinal disease. In the absence of red-flag findings, the most common cause for sciatica is lumbar disc herniation. Symptoms that increase the specificity of radicular pain due to lumbar disk herniation include pain that is worse in the leg than in the back, a typical dermatomal distribution of neurological symptoms, and pain that is worse with the Valsalva manoeuver. Imaging is indicated only in patients with a “red-flag” condition or in cases where disc surgery is considered.