Erector spinae

Three columns known as iliocostalis, longissimus and spinalis

Back · intrinsic (deep) muscle of the spine

A group of long muscles that run in a groove on each side of the vertebral column from the sacrum to the skull. They arise from a common tendon at the lower back and split into three columns, from the outside in: iliocostalis, longissimus and spinalis. They straighten the spine, bend it sideways and control it as you lean forward, and are the muscles that ache in most bouts of low back pain.

How to spot them

▸Two thick vertical ridges on either side of the lumbar spine, wrapped in the thoracolumbar fascia
▸Three parallel columns: iliocostalis lateral, longissimus in the middle, spinalis medial (I Love Spinach)
▸One tendon of common origin from the sacrum, iliac crest and lower vertebrae
▸Supplied by the posterior rami of spinal nerves

What to know

Vertical muscle columns on each side of the spine, running from the sacrum up to the base of the skull and the ribs

Erector spinae — the main extensors of the spine.

Three columns arranged from lateral to medial, whose names mean of the rib and hip, longest, and of the spine

Erector spinae — iliocostalis, longissimus and spinalis; the mnemonic is I Love Spinach.

They contract to straighten the trunk from a stoop, and control the descent as the body bends forward

Erector spinae — extension of the spine, working eccentrically in forward flexion.

Their common tendon takes origin from the sacrum, the back of the iliac crest and the lumbar spinous processes, and is fused with the thoracolumbar fascia

Erector spinae — the common tendinous origin.

Spasm of these muscles is a frequent cause of low back pain, and they are supplied by the back branches of the spinal nerves

Erector spinae — posterior rami of spinal nerves.

Runs in a gutter formed by the spinous processes medially and the angles of the ribs laterally, beneath the thoracolumbar fascia

Erector spinae — an injection plane for the ESP block.

The intermediate column extends from the sacrum up to the mastoid process behind the ear

Erector spinae — the longissimus is the longest of the three columns.

Key ideas

As you bend forward the erector spinae lengthens under tension to lower the trunk in a controlled way, and at full flexion they go silent and the ligaments of the back take the load; that flexion-relaxation is why lifting with a very rounded back is risky.
A plane of fascia beneath the muscle is used by anaesthetists for the erector spinae plane block, a way of numbing the chest and abdominal wall.

Quick-fire facts

•Origin: a common tendon from the sacrum, the posterior part of the iliac crest, the spinous processes of the lower thoracic and lumbar vertebrae and the supraspinous and sacroiliac ligaments
•Iliocostalis (lateral): inserts into the angles of the ribs and the cervical transverse processes
•Longissimus (intermediate): inserts into the transverse processes, the ribs and, at the top, the mastoid process of the skull
•Spinalis (medial): inserts into the spinous processes of the upper thoracic and cervical vertebrae and, sometimes, the skull
•Action: acting together, extend the vertebral column and head; acting on one side, bend the trunk sideways
•Nerve supply: posterior rami of the spinal nerves
•The old name for the lower part is the sacrospinalis
•Each column is divided into regional parts, such as iliocostalis lumborum, thoracis and cervicis
•Deeper than it are the transversospinalis muscles (semispinalis, multifidus, rotatores)

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Sources

TeachMeAnatomy — Intrinsic muscles of the back