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.

Muscle Attachments

Origin

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

Insertion

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

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

Lateral flexion of the vertebral column

Muscle Nerve Supply

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

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