Overview of anatomy
Iliocostalis is part of the erector spinae group, which also includes longissimus and spinalis. Iliocostalis, like the others, has 3 sections. All 9 sections of the erector spinae are gathered into a fascial compartment that extends along the spine.
It is confusing to look at realistic illustrations of these muscles. Some Illustrations show the wad of muscle along the spine. Some of them show the muscles in strips, without gathering them into paraspinal compartments.
Instead, I’d like to focus on the attachments and joints they cross using string diagrams.
Iliocostalis has 3 sections extending from the pelvis to the mid-cervical vertebrae. Each section attaches to the upper 6 ribs, the lower 6 ribs, or both. On the ribs, they attach to the lateral angle, which is that little corner on each rib along the shoulder blade.
Ribs are quite flexible, which is essential to breathing. Erector spine are very active when coughing or defecating. Also, the iliocostalis lumborum is very active at the end ranges of labored breathing. This muscle stabilizes the lateral, posterior ribs, especially when bending over or twisting.
Iliocostalis cervicis attaches to vertebrae C3-C6 and ribs R3-R6.
Illustrations and text vary a great deal on this particular section of the erector spinae. Some texts refer to the upper attachment at C7 whereas most refer to this muscle skipping C7. In addition, the same sort of discrepancy is true of the lower attachment. Most texts say that the lower attachment extends is R3-R6. Some claim that it is the upper 6 ribs or only R4-R6.
Iliocostalis cervicis is one of several muscles that extend the upper thoracic and lower cervical vertebrae. Also, it is one of the many muscles that skip over C7 in that action.
Iliocostalis thoracis originates on the lateral angle of the lower 6 ribs and inserts on the lateral angle of the upper 6 ribs. It is mostly active in the extension of the spine and lateral flexion of the spine.
Iliocostalis lumborum originates on the lower lumbar vertebrae, sacrum and ilium through the thoracolumbar fascia. It inserts on the lateral angle of the lower six ribs.
This muscle extends and laterally flexes the lower spine. It is also quite active in labored breathing, coughing and defecation. It is also active in other motions that depress the lower ribs.
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Tony Preston has a practice in Atlanta, Georgia, where he sees clients. He has written and taught about anatomy, trigger points, and cranial therapies since the mid-90s.
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