What physical finding is associated with a herniated disc at the S1 root?

A positive straight leg raise (SLR) test is associated with a herniated disc at the S1 root because this test assesses for nerve root irritation or compression, typically caused by a herniated disc. When the leg is raised straight while the patient is supine, pain may radiate down the leg if the S1 nerve root is affected, indicating that the sciatic nerve or its roots, including S1, may be compressed.

This sign is particularly relevant because the S1 nerve root is involved in the sensation and motor function of the posterior leg and lateral foot, as well as some control over plantar flexion. When a herniation occurs in the lumbar spine, it may protrude posterolaterally and impinge on the S1 nerve root, leading to the characteristic symptoms that would trigger a positive SLR.

In contrast, other findings like weakness of dorsiflexion are more specific to L4-L5 nerve root involvement, while decreased sensation of the anterior thigh is associated with the L2-L3 nerve roots rather than S1. A normal neurologic examination would not typically suggest the presence of a herniated disc affecting the S1 root, as there would likely be some deficits present. Therefore,