An intercostal muscle strain refers to a muscle injury between two or more ribs. The intercostal muscles, commonly referred to simply as the intercostals, connect the ribs and help make up the chest wall. When these muscles overstretch or tear, they can cause significant pain in the mid- and upper back.

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Intercostal muscle strain is a common injury in athletics and hard labor. It is not typically caused by everyday activity. While an intercostal muscle injury can cause intense pain, most cases are fully healed within 6 to 8 weeks.


What Are the Intercostal Muscles?

There are 11 sets of intercostal muscles on each side of the rib cage, and each set is located between adjacent ribs in the upper- and mid-back.

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Each set of intercostal muscles consists of the following:

  • External intercostal muscles are the outermost intercostals, responsible for expanding the chest during breathing to help inhale air and allow for full, deep breaths.1 The external intercostals originate at the lower edge of one rib and run diagonally forward to attach to the upper edge of the rib below, and are found in the back, sides, and most of the front of the rib cage.2
  • Internal intercostal muscles sit directly underneath the external intercostals and help collapse the chest during breathing to exhale air. 1 The intercostal muscle fibers run perpendicular to the external intercostals, moving diagonally from front to back along the ribs, and are found in the entire rib cage.2
  • Innermost intercostal muscles sit directly underneath and run parallel to the internal intercostal muscles, and run from the back of the rib cage to each side. The intercostal veins, arteries, and nerves are typically found between the internal and innermost intercostal muscles.

In addition to aiding in breathing, the intercostal muscles also help stabilize the rib cage as the upper body twists or bends forward, backward, or to the side. While the intercostal muscles do not connect directly to the spine, their stabilizing role in the rib cage assists in maintaining posture and keeping the back strong and healthy.

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When to See a Doctor

Some cases of intercostal muscle strain may be so mild that pain or stiffness alleviates within a few days, and thus does not necessitate medical attention. It is advisable to see a doctor if upper back pain persists for several days or begins to interfere with daily activity, such as going to work or sleeping.

Additionally, medical attention is advisable if upper back pain is so severe that it causes difficulty breathing or makes everyday movements feel impossible, such as lying down or moving from standing to sitting. Severe pain that occurs following a traumatic injury, such as a fall or car accident, should be promptly addressed by a doctor.


  • 1.Bakkum BW, Cramer GC. Muscles that influence the spine. In: Cramer GC, Darby SA, Clinical Anatomy of the Spine, Spinal Cord, and Ans, 3rd Edition. St. Louis, MO: Elsevier; 2014: 122.
  • 2.Rakovich G, Fréchette É, Deslauriers J. Thoracic surgical anatomy and procedures. In: Lewis MI, McKenna RJ, Medical Management of the Thoracic Surgery Patient. Philadelphia, PA: Saunders, Elsevier Inc; 2010. Accessed September 5, 2017.