Anatomy, Bony Pelvis and Lower Limb: Piriformis Muscle

Excerpt

The piriformis is a flat, pear-shaped muscle located in the gluteal region. This muscle originates from several anatomical locations, namely, the anterior surface of the sacrum, the spinal part of the gluteal muscles, the superior gluteal surface of the ilium near the margin of the greater sciatic notch, the capsule of the adjacent sacroiliac joint, and sometimes, the sacrotuberous ligament.

The piriformis exits the pelvis through the greater sciatic notch before entering the gluteal region. The muscle courses parallel to the posterior margin of the gluteus medius and deep to the gluteus maximus. The tendons of the piriformis, obturator internus, and inferior and superior gemelli fuse before inserting on the superior aspect of the femur's greater trochanter (see Image. Right Femur Anatomy). The piriformis abuts the posterior wall of the pelvis and the posterior wall of the hip joint.

This muscle is one of the 6 short external thigh rotators (see Image. Short External Thigh Rotators). More importantly, the piriformis is a key anatomic structure in that some gluteal nerves and blood vessels are named based on their spatial relationship with this muscle.

This article discusses the piriformis muscle's anatomy and its clinical relevance.