Sternum lies in the midline of the anterior chest wall. It is a flat bone and it consists of three parts
1. Manubrium
2.  Body
3.  Xiphoid process


breast bone


The manubrium is the upper part of the sternum and its articulate with the body through a manubriosternal joint.
It also articulates with clavicle and first costal cartilage.

Location of manubrium
It lies opposite to the third and fourth thoracic vertebrae.

Body of sternum

This is the central portion of the sternum and its articulates above with the manubrium and below with the xiphoid process through a manubriosternal and xiphisternal joint respectively.
It also articulates with the 2nd to 7th costal cartilages.

Xiphoid process of the sternum

It is the lower part of the sternum and it is a cartilage plate which ossifies during adult life. It is free so no ribs and costal cartilages are attached to it.

Angle of Louis

The angle of Louis which is also known as the sternal angle formed by the articulation of manubrium with the body of the sternum.
It is found at the level of 2nd costal cartilages.

Location of the sternal angle

It lies opposite to the intervertebral disc between the fourth and 5th thoracic vertebrae.

Sternum development

The sternum develops from two cartilaginous bars connected to cartilages of ribs. These two cartilaginous bars fuse together and form cartilaginous sternum. The cartilaginous sternum is then ossified from six centres. The manubrium oddities from one centre, the body ossifies from four centres, and the xiphoid process ossified from one centre.

These ossification centres from which the sternum ossified appears in the intervals between the articular depression for the costal cartilages.

In early life, the sternum body is divided into four parts while in adults the sternum body is divided into three parts.

Bone marrow biopsy

As we know that sternum contains bone marrow and due to this property it is sometimes used as a site for marrow biopsy. The sternum is the best site for bone marrow biopsy in patients who have high BMI.

Sternal opening

The sternal opening is a rare disorder in which a single round hole is present in the sternum from birth. The sternal opening can often be mistaken for bullet holes.

Fractures of sternum

Fractures of this bone are uncommon. Fractures in the sternum may result from trauma. The sternal angle or angle of Louis is the site where the sternal fracture occurs mostly. Some studies show that repeated punches to the sternum area may also cause a fractured sternum.


The manubriosternal joint dislocation is rare but occurs due to severe trauma. If there is a precondition of Arthritis then minor trauma may also cause manubriosternal dislocation.


In some types of surgeries such as cardiothoracic surgery, the surgeons cut the breast bone to gain access to the structure in thoracic regions. this process is known as a sternotomy.

Sternum pain

It is a Pain or discomfort in the area of the chest that contains breast bone and ribs. As we know that breast bone is located near the heart so people may confuse it with more general chest pain.

Causes of pain

The pain in the breast bone is usually caused by bone and muscles near the breast bone, not by the sternum itself. Some of the causes are

1. Costochondritis
2.  Sternoclavicular joint injury
3.   Hernia
4.   Collarbone injuries
5.   Acid reflux
6.   Muscular strain.

Symptoms of sternum pain

Symptoms of sternum pain are
1. Discomfort in ribs
2.  Pain worsens during cough
3.  Aching pain
4.  Swelling
5.  Stiffness in shoulder joint
6.  Difficulty in breathing
7.  Popping sensation in joints near the sternum
8.  Belching
9.  Heartburn
10.  Throwing up blood
11.  Feeling to pull.


This condition occurs when the cartilage between the ribs and breast bone become inflamed. Costochondritis is the most common cause of sternal pain.  This condition may sometimes occur as a result of osteoarthritis.

Symptoms of costochondritis

1. Sharp pain
2.  Pain worsens with deep breath and cough
3.   Discomfort in ribs.

Sternoclavicular joint injury

The sternoclavicular joint is the joint between the breast bone and collar bones. Injuries to this joint may cause pain in the sternum.  If the pain occurs due to this condition then the following symptoms appear

1. Mild pain
2.  Swelling in the upper chest area
3.   Pain when moving the shoulder
4.   Popping around the joint.

Collar bone injuries

This bone is not part of the breast bone but it is connected to the breast bone by cartilages. Therefore injuries to this bone may cause pain in sternum.

1. Trauma
2.  Infections
3.  Arthritis

1. Swelling in the upper chest area
2.  Severe pain when a person tries to raise the arm
3.  Sagging of the shoulder
4.  Grinding in the shoulder joint


Hernias are not responsible for sternal pain but may cause substernal pain. There are many types of hernias. The hernia that is responsible for substernal pain is a hiatal hernia.  This type of hernia occurs when the stomach moves out of its normal position.

1. heartburn
2.  Vomiting blood
3.   Burping
4.  Trouble Swallowing

Acid reflux

Acid reflux occurs in peoples with gastroesophageal reflux disease. In this condition, stomach acid wears away the lining of the windpipe. Acid reflux causes substernal pain, not sternal pain.

Summary of sternum

the breast bone is a bone that lies in the midline of the anterior chest wall. According to the classification of bones, it is a flat bone. This bone consist of three parts that are manubrium, body, and the xiphoid process. Manubrium articulates with the body through the manubriosternal joint and the xiphoid process articulates with the body through a xiphisternal joint. The manubrium is the upper part of the bone, the body is the middle part while the xiphoid process is the lower part of the bone. Another important structure that is present in the breastbone is an angle of Louis or a sternal angle. The angle of Louis is formed by the articulation of manubrium and body of the breast bone. The angle of Louis lies opposite the intervertebral disc between the 4th and 5th ribs. This one is very important because it contains bone marrow and can be used for bone marrow biopsy.