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What is the sternum?

The sternum is also known as breastbone. It is a flat, bony plate located in the center of the thorax (chest). The shape of the sternum is like a capital "T". The ribs are connected to the sternum in the front and to the spine at the back, with the help of cartilages. The sternum also is connected with the clavicles on each side.

Anatomically, the sternum is divided into three regions:

  • The manubrium
  • The body
  • The xiphoid process

The major function of the sternum and the thorax are to protect the heart, lungs, and the great blood vessels from any trauma.

Why does the sternum crack?

A cracking sound from the sternum is associated with the joints that connect the ribs and the clavicle to the sternum. The problem is usually with the joints that connect the ribs and not the ones that connect the clavicles.

Cracking of the sternum is usually accompanied by pain, tenderness and in some cases joint swelling.

However, the exact mechanism that produces this cracking sound is not known.

It may be due to partial dislocation, the "snapping" of ligaments or tendons, or gas bubbles released from the joint fluid.

The cracking of the sternum usually occurs with deep breathing or stretching the arms wildly. In some cases, the cracking of the sternum is spontaneous.

Usually it is not considered to be a medical problem, unless you have pain, reduced joint movement, stiffness or even swelling of the joint.

If any of these symptoms occur after the cracking of the sternum, you should seek medical help and request further examinations.

What causes the sternum to crack?

The main causes are:

  • Trauma to the chest area like car accidents, falls, or assault.
  • Muscle spasm, which can even cause a subluxation of the joints. Chest pain is always present.
  • Rheumatoid arthritis - doesn't typically affect these joints, but in widespread cases the degeneration of the joints can cause them to crack.
  • Tietze's Syndrome usually affects the second and third ribs. It is the inflammation of the costal cartilage, just like costochondritis. Pain, stiffness and even swelling are present.
  • Physical strain is seen in case of activities that put pressure on the chest wall like excessive weight lifting.
  • Costochondritis is the inflammation of the costal cartilage. Usually affects the fourth, fifth and sixth ribs. Pain and tenderness are common, while swelling of the joints is very rare.
  • Calcification of the costal cartilage.

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