|The piriformis and nearby muscles|
|Muscles of the gluteal and posterior femoral regions, piriformis labeled|
|Gray's||subject #128 476|
|Artery:||Inferior gluteal artery , Lateral sacral artery, Superior gluteal artery,|
|Nerve:||nerve to the Piriformis (L5, S1, and S2 nerve roots)|
|Action:||rotate laterally (outward) the thigh|
Origin and insertion
It originates from the anterior (front) part of the sacrum, the part of the spine in the gluteal region, and from the superior margin of the greater sciatic notch (as well as the sacro-iliac joint capsule and the sacrotuberous ligament).
Shape and location
The piriformis is a flat muscle, pyramidal in shape, lying almost parallel with the posterior margin of the gluteus medius.
It arises from the front of the sacrum by three fleshy digitations, attached to the portions of bone between the first, second, third, and fourth anterior sacral foramina, and to the grooves leading from the foramina: a few fibers also arise from the margin of the greater sciatic foramen, and from the anterior surface of the sacrotuberous ligament.
The muscle passes out of the pelvis through the greater sciatic foramen, the upper part of which it fills, and is inserted by a rounded tendon into the upper border of the greater trochanter behind, but often partly blended with, the common tendon of the obturator internus and gemelli.
It is frequently pierced by the common peroneal nerve (fibular) when the sciatic nerve bifurcates prior to exiting the greater sciatic foramen. Thus the Piriformis is divided more or less into two parts.
It may have only one or two sacral attachments or be inserted in to the capsule of the hip-joint.
It may be absent.
This syndrome occurs when the piriformis irritates the sciatic nerve, which comes into the gluteal region beneath the muscle, causing pain in the buttocks and referred pain along the sciatic nerve. This referred pain is known as "sciatica." 15% of the population has their sciatic nerve coursing through the piriformis muscle. This subgroup of the population is predisposed to developing sciatica.
Sacrum, pelvic surface.
- SUNY Labs 13:st-0408 - "Gluteal Region: Muscles"
- SUNY Labs 43:15-0101 - "The Female Pelvis: The Posterolateral Pelvic Wall"
- -1281753008 at GPnotebook
- LUC pirf
- - "Piriformis Muscle Stretch, Biomechanics & Piriformis-Sciatic Nerve Relationship Graphics
This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.