Piriformis (Musculus piriformis)
Educational content only — not medical advice.
Anatomy
A pear-shaped muscle leaving the pelvis through the greater sciatic foramen to the greater trochanter; the sciatic nerve passes beneath it or (in ~15%) pierces its fibres — the key to gluteal anatomy.
Origin & insertion
Anterior sacral surface between the second and fourth anterior sacral foramina.
Action
Laterally rotates and stabilises the femoral head; its borders split the greater sciatic foramen into the suprapiriform and infrapiriform compartments.
Innervation
Direct branches from the sacral plexus (S1–S2).
Clinical notes
Piriformis syndrome entraps the sciatic nerve in the foramen producing "sciatica without spinal injury"; tested by the FAIR manoeuvre (flexion-adduction-internal rotation).
Related structures
Educational references
FAQ
What is the role of the Piriformis?
A pear-shaped muscle leaving the pelvis through the greater sciatic foramen to the greater trochanter; the sciatic nerve passes beneath it or (in ~15%) pierces its fibres — the key to gluteal anatomy.
Why is the Piriformis clinically important?
Piriformis syndrome entraps the sciatic nerve in the foramen producing "sciatica without spinal injury"; tested by the FAIR manoeuvre (flexion-adduction-internal rotation).
Source & license
BodyParts3D, © The Database Center for Life Science licensed under CC Attribution 4.0 International (https://creativecommons.org/licenses/by/4.0/). license details