Many people have heard of the serratus anterior muscle, but this article will dive into the anatomy, function, and pain of its often-forgotten relative, the serratus posterior inferior (SPI).
Serratus Posterior Inferior Anatomy
Origin:
The SPI originates from the spinous processes of the lower thoracic and upper lumbar spine, specifically T11, T12, L1, and L2.

Insertion:
Via four separate tendons, the different muscle bellies span superolaterally to attach on ribs 9-12 (see image - [1]).
Muscle action:
When the SPI contracts, it depresses the rib cage, or brings it down. This is especially evident during forced exhalation, where we are breathing out. For this reason, it is considered an accessory muscle of respiration.
The twin brother of the SPI is the serratus posterior superior, which helps to elevate the rib cage when it contracts. Meanwhile, the SPI would be relaxing, or lengthening, during inhalation. These two muscles act as complementary opposites when we breathe, aiding the diaphragm to bring air in and out of our lungs.

[2]
Serratus Posterior Inferior Pain and Dysfunction
Pain and dysfunction in the serratus posterior inferior usually stays localized to that area. Some muscles have referral patterns. Referral patterns are predictable patterns that an angry muscle follows when there is dysfunction, and it presents as pain somewhere else in the body. One good example of this is the rotator cuff. Although the muscles of the rotator cuff are found on the posterior shoulder, many people with rotator cuff tears report pain on the front of their arm, in the crease between their bicep and deltoid muscles.
With the SPI, this is not the case. If you have pain in this area, the SPI may be the culprit. Unfortunately, this is a deep muscle. It lies deep (underneath) the lats, and superficial (above) the erector spinae group. This means you cannot see it, making it hard to identify.

[3]
Another area of consideration is that this area can be a referral site for visceral dysfunction. Most commonly, this is an area where people with kidney stones may feel pain. If you have intense pain that is unremitting and doesn’t change when you change positions, that could be a sign of pain that is not muscular. In this case, you should see a medical professional ASAP.
Assess Serratus Posterior Inferior Pain
One way to assess SPI pain or dysfunction is to take some deep breaths. This is a technique called “box breathing” that I like to use with patients. It involves four phases: inhale, hold, exhale, hold. Each phase will be an equal length.
-
Sit in a comfortable posture that allows you to fully expand your lungs
-
Take a full, deep inhale, allowing your lungs to expand fully for 3-4 seconds
-
pause for 3-4 seconds
-
slowly exhale for 3-4 seconds
-
pause 3-4 seconds.

[4]
This breathing technique can be used as a diagnostic tool, and a treatment! As a diagnostic, it can help to localize tight muscles that are involved with breathing. In this case, if you feel tightness in your lower back when you are inhaling, you may have some tightness in the SPI. This is because the SPI will be maximally stretched when the lungs are filled with air and the rib cage is expanded. If you do a forceful exhale, you may feel some tightness in that area as well.
The good news is, this breathing exercise can be used to reduce tightness in the SPI or any accessory breathing muscle. I recommend sitting in a comfortable position and completing 10-12 rounds of this breathing cycle. Think of this exercise like a stretch, because that’s exactly what it is! As the lungs fully expand, the origin and insertion of the SPI spread apart, giving the muscle a good stretch.
This exercise can also activate the parasympathetic nervous system, putting the body into a calm state. This can reduce the perception of pain from different areas of the body. Box breathing is a good tool for the toolbox to combat pain and dysfunction in the muscles of respiration.
Serratus Posterior Inferior Pain Relief
Another intervention to try if you have some pain in this area is to use a massage device like the QL Claw. A good technique for this muscle is to identify where the SPI is. I would do this by finding the bottom two ribs (ribs 11 and 12) on your back side, and tracing a path to the spine. Then, you can rest your body on the claw and do some deep breathing while the claw puts some manual force through the muscle. As you inhale, allow your body to relax into the claw. This can help to provide pain relief and decrease muscle tightness.
Sources:
[1] https://en.wikipedia.org/wiki/Serratus_posterior_inferior_muscle
[2] https://study.com/academy/lesson/serratus-posterior-muscles-function-innervation.html
[3] Davies, Clair, and Amber Davies. The Trigger Point Therapy Workbook: Your Self-Treatment Guide for Pain Relief. 3rd ed., New Harbinger Publications, Inc., 2013.
[4] https://www.getcognito.ca/blog/what-is-box-breathing
I already gave up on ever getting cured of HSV2 because i have try many treatment none of them work out for me i have gone to different hospital they always tell me the same thing there is no cure for herpes, when i came across a post about Dr UMA in the net from a lady called Angela i contacted her and she reassured me with his herbal medicine which i took according to the way he instructed, that how i was cured. I doubted at first because i have been to a whole lot of reputable doctors, tried a lot of medicines but none was able to cure me. so i decided to listen to him and he commenced treatment, and under two weeks i was totally free from Herpes. i want to say a very big thank you to DR UMA for what he has done in my life. feel free to leave him a message on email dr.umaherbalcenter@gmail.com or also Whats-app him +2347035619585.. he also cure all this 1.HIV 2.HIV HPV 3 .ALS 4. BED WETTING DIABETES.