|Origin||Iliocostalis cervicis angle of ribs 3-6|
Iliocostalis thoracis angle of ribs 7-12
Iliocostalis lumborum medial end of iliac crest, lateral crest of sacrum, & thoracolumbar fascia
|Insertion||Iliocostalis cervicis posterior tubercle of the transverse process of C4-C6|
Iliocostalis thoracis transverse process of C7 & angles of the ribs 1-6
Iliocostalis lumborum transverse processes of L1-L4 & angles of ribs 4-12
|Action||Unilateral contraction lateral flexion of the trunk/vertebral column & weak lateral flexion at the base of the neck (below C4)|
Bilateral contraction extends the trunk/vertebral column & weak extension of the base of the neck (below C4)
|Nerve||Lateral branches of the posterior rami of the spinal nerves|
|Artery||Dorsal branches of the posterior intercostal, subcostal, lumbar & lateral sacral arteries|
Location & Overview
The iliocostalis muscle is a part of the deep musculature of the back and one of the three muscles that make up the erector spinae group, alongside the spinalis and longissimus. Out of these three, the iliocostalis is the most lateral. The iliocostalis is separated into three distinct regions based on their point of origin: iliocostalis cervicis, iliocostalis thoracis, and iliocostalis lumborum. The lumborum section is most inferior (lowest), and the capitis section is the most superior (highest). The cervicis section is in the middle. The different sections are displayed in the below images  .
The iliocostalis muscle plays an important role in various sporting activities, such as powerlifting, where it helps to maintain spinal extension during competition lifts like the deadlift. It also aids in stabilising and supporting the spine during gymnastics movements. In swimming, it helps to maintain proper body position, especially during freestyle and backstroke. The iliocostalis muscle is also important for day-to-day activities, such as lifting objects, by stabilizing the spine and maintaining proper posture. It also assists with less strenuous tasks, such as sitting upright and standing upright.
Origin & Insertion
The points of origin and insertion of the iliocostalis muscle differ among its various segments. The specifics are as follows:
The iliocostalis lumborum originates at the medial end and dorsal segment of the iliac crest and the lateral crest of the sacrum. It inserts at the lumbar transverse processes of L1 to L4, the angles of ribs 4 to 12, and the thoracolumbar fascia  .
The actions of the iliocostalis muscle vary based on whether it contracts unilaterally or bilaterally. When only one side contracts, the result is lateral flexion of the trunk and vertebral column. When both sides contract together, it causes extension of the trunk and vertebral column. The cervicis segment of the muscle extends from the cervical vertebrae to the fourth cervical vertebra (C4), offering weak support for lateral flexion at the neck’s base during unilateral contractions and weak extension at the neck’s base during bilateral contractions  .
Blood is supplies to the iliocostalis through dorsal branches of the posterior intercostal, subcostal, lumbar and lateral sacral arteries.
Want some flashcards to help you remember this information? Then click the link below:
|↑1, ↑3, ↑5, ↑7||Henson B, Kadiyala B, Edens MA. Anatomy, Back, Muscles. [Updated 2022 Aug 25]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK537074/|
|↑2, ↑4, ↑6, ↑8, ↑10, ↑12||Moore KL, Agur AMR, Dalley AF. Clinically Oriented Anatomy. 8th ed. Philadelphia: Lippincot Williams & Wilkins; 2017.|
|↑9, ↑11||Chaitow, Leon, and DeLany, Judith (2011), Clinical Application of Neuromuscular Techniques, Volume 2 (Second Edition), Oxford: Churchill Livingstone, ISBN 978-0-443-06815-7|