intercostal muscles, nerve, spaces and strain

Intercostal spaces

To understand intercostal muscles first we have to know intercostal spaces. Intercostal spaces are spaces between the ribs which contains muscles. These muscles are external intercostal, internal intercostal, and innermost intercostal.

The most internal muscle in these muscles is lined internally by the endothoracic fascia which is lined internally by parietal pleura.

Blood vessels and nerves run between internal intercostal and innermost intercostal.

Intercostal muscles

These are three muscles which are

1. External intercostal muscles
2. Internal intercostal muscles
3. Innermost intercostal muscles

External intercostal muscles

These muscles form the superficial layer and their fibers run downward and forward. These muscles run from the inferior border of the rib above to the superior border of the rib below.
These muscles when reached to the costal cartilages they are replaced by an aponeurosis.

Internal intercostal muscles

These muscles form the intermediate layer and their fibers are directed downward and backward. These muscles run from the subcostal groove of the rib above to the upper border of the rib below.

Innermost intercostal muscles

These muscles form the deepest layer and cross more than one intercostal space within the ribs.


internally   Endothoracic facia
externally   intercostal vessels and nerves


These muscles when contact they pull the ribs nearer to one another. If the first rib is fixed by scalene muscle then the muscles will raise the 2nd to 12th rib toward the 1st rib and this occurs during inspiration.

If the 12th rib is fixed then the contraction of these muscles will lower 1st to 11th ribs and this occurs during expiration.

Nerve supply of intercostal muscles

These muscles are supplied by intercostal nerves which come from the rami.

The intercostal nerves run between the internal intercostal and innermost intercostal. These nerves are located below the arteries.

Intercostal nerves

Intercostal nerves are part of the nervous that arises from the anterior rami of the thoracic spinal nerve. These nerves arise from T1 to T11 thoracic spinal nerves. These nerves are distributed to the thoracic pleura, and peritoneum. These nerves differ from other spinal nerves and do not form plexus.

Intercostal nerves arise from the somatic nervous system and control the contraction of muscles and provide specific information regarding parietal pleura and skin.

1st thoracic nerve
The anterior division of the first thoracic nerve gives two branches one is smaller and the other is large. The large branch leaves the thorax in front of the neck of the first rib and enters the brachial plexus. The smaller branch is the intercostal nerve that runs along with the first intercostal space and ends on the front of the chest.

2nd to 6th upper thoracic nerves
The anterior division of 2nd to 6th upper thoracic nerve and the branch of first thoracic nerve confined to the chest wall and are termed as thoracic intercostal nerves. These nerves pass forward and below the intercostal blood vessels in the intercostal spaces. At the back first, they lie between the posterior intercostal membrane and pleura but soon they run between the innermost intercostal and internal intercostal muscles. Near the sternum, they cross in front of the internal mammary artery and supply the integument of the front of the thorax.

1. Lateral cutaneous branches
2.  Anterior branches
3.  Posterior branches

7th to 11 lower thoracic nerves
The anterior division of the 7th to 11th thoracic intercostal nerves continued from the intercostal spaces into the abdominal wall. Due to this reason, they are named as thoracoabdominal nerves or thoracoabdominal intercostal nerves.

Intercostal muscles strain

It is an injury that affects the muscles between two or more ribs. Intercostal muscles attached to the ribs and have functions to build a chest wall and assist in breathing. When these muscles get twisted or strained than it can tear and cause intercostal muscle strain.

1. Sharp upper back pain
2.  Rib pain
3.  Severe or sudden pain
4.   Worsening of pain after repetitive movement
5.  Stiffness and tension in the muscles
6.  Spasm of the intercostal muscles
7.   Tenderness in the areas between the ribs.

1. A direct blow to the ribcage
2.  An impact blow from contact sport such as football
3.  Twisting the torso beyond the normal range
4.  Forceful twisting
5.   Reaching overhead
6.   Repetitive forceful movement

A mild injury causes a low level of pain that goes away within a few days. If the pain is severe and interferes with sleep and daily activities then see a doctor.

Diagnosis involves a physical exam that checks the limitation of movement asses tender areas. X rays scan or MRI scan may be ordered.

Intercostal neuralgia

It is also known as chest wall pain. It is a condition that causes pain along the nerves in the intercostal spaces between the ribs. It is caused when a nerve in the area is compressed by a rib cage.

Symptoms of the intercostal neuralgia are

1.  Pain that is dull and constant
2.   Pain may be described as sharp, tearing, aching.
3.   Pain wrapped around the upper chest like a band.
4.   Pain during breathing, sneezing and laughing
5.    Pain in the back
6.    Pain in the sides of the ribs
7.    Difficulty in moving in severe cases

When to see a doctor?
If you experienced unexplained severe pain in the rib cage,  chest pain, difficulty in breathing, and shortness of breath, it is important to see a doctor and seek immediate medical care.

Risk factors
Possible risk factors for intercostal neuralgia are
1. Injury of the nerves
2.  Inflammation of the nerves
3.  Injury or inflammation of muscles
4.   Injury or inflammation of the cartilages and ligaments in the ribcage and middle spine area

Any chest wall pain you experienced should be evaluated by a doctor. Sometimes the doctor referred to an X-ray or MRI scan.

Local anesthetic or corticosteroids is injected around the affected nerve which relieves the pain by blocking the nerves.

NSAIDs may be used to reduce inflammation and pain.

Radiofrequency lesioning can also be used.

It is very easy to prevent intercostal neuralgia than to treat. The preventive measures include

1.  Active lifestyle
2.  Preventing herpes
3.   Healthy diet
4.   Limit smoking
5.   Limit alcohol
6.   Regular exercise
7.   Strengthening the back muscles.


There are three muscles that are present in the intercostal spaces and they are external intercostal, internal intercostal, and innermost intercostal.