Piriformis syndrome is a condition in which the piriformis muscle irritates the sciatic nerve, potentially causing referred pain along the course of the sciatic nerve. Anatomically, the piriformis muscle lies diagonally deep in the buttock below the gluteal muscles. The sciatic nerve typically passes directly underneath the piriformis muscle; when the piriformis muscle spasms, it can compress the sciatic nerve.
Patient complaints of sciatica or of pain deep in the buttocks that worsens by sitting and/or climbing stairs can indicate piriformis syndrome.
