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Iliocostalis lumborum muscle icon

Iliocostalis Lumborum Muscle

Description, Attachments, Actions, and Innervation

Muscle Description

The iliocostalis lumborum muscle lies lateral to the longissimus muscle group and deep to the serratus posterior muscle. It is part of the erector spinae muscles, which function to straighten and laterally flex the vertebrae column.

Iliocostalis Lumborum Muscle - superficial view
Iliocostalis Lumborum Muscle - deep view

Muscle Attachments


The iliocostalis lumborum muscle originates from the medial and lateral sacral crests and medial iliac crest.


The iliocostalis lumborum inserts on the angles of ribs 6 or 7 – 12.

Iliocostalis Lumborum Muscle - attachments (origin and insertion)

Muscle Actions

Bilaterally muscle contraction (both muscles contract): Extend the vertebral column.

Unilateral muscle contraction (one muscle contracts): Laterally flex the vertebral column to the same side.

Extension of the vertebral column

Flexion of the vertebral column by iliocostalis lumborum muscle

Lateral flexion of the vertebral column

Lateral flexion of the vertebral column by iliocostalis lumborum muscle

Muscle Nerve Supply

Dorsal primary rami of thoracic and lumbar spinal nerves (T7 to L3).

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