Piriformis muscle

From Wikipedia, the free encyclopedia

Piriformis muscle
The piriformis and nearby muscles
Muscles of the gluteal and posterior femoral regions, piriformis labeled
Latin	musculus piriformis
Gray's	subject #128 476
Origin	sacrum
Insertion	greater trochanter
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
Dorlands /Elsevier	m_22/12550205

The piriformis (from Latin piriformis = "pear shaped") is a muscle in the gluteal region of the lower limb.

Contents 1 Origin and insertion 2 Shape and location 3 Variations 4 Clinicals 5 Additional images 6 External links 7 References

[edit] 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).

It exits the pelvis through the greater sciatic foramen to insert on the greater trochanter of the femur.

Its tendon often joins with the tendons of the superior gemellus, inferior gemellus, and obturator internus muscles prior to insertion.

[edit] Shape and location

The piriformis is a flat muscle, pyramidal in shape, lying almost parallel with the posterior margin of the gluteus medius.

It is situated partly within the pelvis against its posterior wall, and partly at the back of the hip-joint.

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.

[edit] Variations

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 be united with the gluteus medius, or send fibers to the gluteus minimus or receive fibers from the superior gemellus.

It may have only one or two sacral attachments or be inserted in to the capsule of the hip-joint.

[edit] Clinicals

Main article: Piriformis syndrome

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.^[1] 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.

[edit] Additional images

Sacrum, pelvic surface.	Upper extremity of right femur viewed from behind and above.	Right femur. Anterior surface.	Structures surrounding right hip-joint.
Left Levator ani from within.	The arteries of the gluteal and posterior femoral regions.	Dissection of side wall of pelvis showing sacral and pudendal plexuses.	Nerves of the right lower extremity Posterior view.

[edit] External links

• [1] University of Washington - "Piriformis"
• 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

[edit] References

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.

v • d • e List of muscles of lower limbs ILIAC Region / ILIOPSOAS psoas major/psoas minor - iliacus BUTTOCKS gluteals: (maximus, medius, minimus) - tensor fasciae latae lateral rotator group: piriformis - inferior gemellus - obturator internus - superior gemellus - quadratus femoris THIGH anterior compartment: sartorius - quadriceps (rectus femoris, vastus lateralis, vastus intermedius, vastus medialis) - articularis genu posterior compartment/hamstring: biceps femoris - semitendinosus - semimembranosus medial compartment: pectineus - obturator externus - gracilis - adductor (longus, brevis, magnus) LEG anterior compartment: tibialis anterior - extensor hallucis longus - extensor digitorum longus - peroneus tertius posterior compartment: superficial - calf/triceps surae (gastrocnemius, soleus) - plantaris posterior compartment: deep - tarsal tunnel (flexor hallucis longus, flexor digitorum longus, tibialis posterior) - popliteus lateral compartment: peroneus muscles (longus, brevis) FOOT dorsal - extensor hallucis brevis - extensor digitorum brevis plantar - 1st layer (abductor hallucis, flexor digitorum brevis, abductor digiti minimi) plantar - 2nd layer (quadratus plantae, lumbrical muscle) plantar - 3rd layer (flexor hallucis brevis, adductor hallucis, flexor digiti minimi brevis) plantar - 4th layer (dorsal interossei, plantar interossei)

en:Hruškasta mišica