Anatomy

Sternal Angle

Anatomy

/ster-nl ang-gul/

Eponym: Angle of Louis

Structure:

The sternal angle is the palpable transverse ridge formed at the junction of the manubrium and the body of the sternum, where these two components lie on slightly different planes and meet at the manubriosternal joint.[1] This joint is typically located at the level of the second costal cartilage and corresponds posteriorly to the intervertebral disc between the fourth and fifth thoracic vertebrae (T4–T5).[1]

The sternal angle is an important surface landmark used to identify the second rib, from which ribs and intercostal spaces are counted.[1] It also serves as a reference point for several internal thoracic structures, including the bifurcation of the trachea, the beginning and end of the aortic arch, and the superior border of the heart.[1] The sternal angle is usually palpable and may be visibly apparent in younger individuals due to slight mobility at the manubriosternal joint during forced respiration.[1]

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Function:

Limited movement at the manubriosternal joint allows for anterosuperior expansion of the thoracic cage during inspiration, contributing to increased thoracic volume.[2] Although overall sternal mobility is restricted by the manubrium, this slight flexibility facilitates normal respiratory mechanics.[2]

Clinically, the sternal angle is a commonly used landmark for auscultation of heart and lung sounds and for interpreting imaging studies of the thorax.[2] In older adults, the manubriosternal joint may become more rigid, and the sternal angle is a frequent site of sternal fracture, which can result in dislocation at this joint.[1]

References:

Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. 6th ed. International ed. Lippincott Williams & Wilkins; 2010.
Ball M, Falkson S, Fakoya A, Adigun O. Anatomy, angle of Louis. In: StatPearls. StatPearls Publishing; 2023.

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