Iliocostalis Lumborum: Learn Your Muscles

Maybe you haven’t heard of the iliocostalis lumborum, but if you have back pain, you need to learn about it. This muscle is located near to the quadratus lumborum, another low back muscle, and they share similar functions. Their locations and jobs are so similar, in fact, that iliocostalis lumborum dysfunction is often misdiagnosed as quadratus lumborum issues.


iliocostalis lumborum
Thanks to Anatomy Expert for the image.

According to Flash Anatomy Muscles Flash Cards, the iliocostalis lumborum originates on the “anterior surface of a broad and thick tendon which originates from the sacrum, spinous processes of the lumbar and 11th and 12th thoracic vertebrae, and from the medial lip of the iliac crest.” All of that looks very complex, so let’s break it down.

First, notice that there are three spots of origin for this muscle. One spot of origin is a tendon that comes off the sacrum (tailbone). Another spot is the bony spine on the back of your lumbar and 11th and 12th thoracic vertebrae. This means that all five of the lumbar vertebrae as well as the two lowest thoracic vertebrae are  points of origin. The final spot is the inside rim of the back of your pelvis.

The iliocostalis lumborum inserts on the inferior borders of the lower 6 or 7 ribs. This means that it inserts on vertebraes T-5 or T-6 through T-12. In this case, “inferior borders” refers to the very bottom edge of these particular ribs.


When both sides of the iliocostalis lumborum act at the same time, they extend the spine. As your head moves behind the line of your spine, you move into spinal extension. This is common when you reach back to stretch in your chair. Also, Cobra pose is a popular yoga pose for spinal extension.

However, when only one side of the iliocostalis lumborum fires, it laterally flexes the spine. Lateral flexion is when your body bends straight to the side. For example, if you were sitting in a chair and wanting to set something on the floor beside you, you would laterally flex and set down the item.

In that example, you are bending and moving your rib cage toward your pelvis. Lateral flexion works the other way, too. You can also move your pelvis toward your ribs. One of the best examples of this type of movement is using your hip to help boost a bag of groceries or a child.

Perhaps you have already noticed that this sounds an awful lot like the quadratus lumborum. The muscles are neighbors and perform similar actions. It has also been noted that the two are somewhat of partners in crime. Frequently, if one of the muscles is acting up, the other one will be, too. It is also possible that, because the quadratus lumborum is more well-known, it gets blamed for ilicostalis lumborum dysfunction.

Common Dysfunction

Unfortunately, the iliocostalis lumborum can be injured simply by performing its standard actions. A reach backward or a simple bend to the side can cause the muscle to spasm and create pain and dysfunction. No matter the cause, the result is back pain.

Restoring or Maintaining Health

As always, I recommend that if you have any sort of pain, you should consult your physician. Your doctor can order the proper tests, medication, and therapy to help relieve your pain.

However, if you’re wanting to do some exercises at home to help strengthen and stretch the iliocostalis lumborum, I have a couple of suggestions. Before you begin, you should be aware that tightness=weakness. This is why you will want to both strengthen and stretch this muscle.

I recommend Triangle pose as an exercise to improve your lateral flexion. Think of other exercises and poses when you bend to the side. These are all probably good for strengthening and stretching. For example, I think Side angle pose would be another good pose.

To improve your spinal extension, you can use any number of yoga poses or Pilates exercises. For example, you could do Bridge poseSphinx pose, Swan dive, or Breast stroke preps. Make sure to draw your belly button to your spine to help support your low back as you work.

More Information

I consulted my Flash Anatomy Muscles Flash Cards. If you really enjoy anatomy and want a tool to help you locate specific muscles correctly, I highly recommend these flash cards. I turn to them any time a client comes in with pain.

Here’s a link to buy them on Amazon. If you purchase them from this link, I earn a small commission.

I want to take a moment to thank you for reading this article. Personally, I enjoy sharing this information with you, and I hope you find it valuable. If you do, please consider supporting this website!

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Sarah Stockett is STOTT certified in Matwork, Reformer, Cadillac, Chair, & Barrels, Injuries & Special Populations, and CORE; a Yoga Alliance RYT-200; and has studied Active Isolated Stretching. When she is not trying to discover the best exercises to get rid of pain, she likes watching movies and travelling with her family.

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