This is the angle formed by the junction of the manubrium and the body of the sternum. A horizontal plane extended backwards to the fourth thoracic interspace marks the boundary between the inferior and superior mediastinum. This angle is also known as the angle of Louis. Other than the xiphoid process, this is the narrowest part of the sternum.

Sternal comes from the Greek word sternon meaning breast. It was first used by Claudius Galen in the 2nd Century. The Latin form sternum, which was not used by the Romans, came into the English in the 17th Century. The term angle arises from the Latin angulus meaning to bend or diverge from a central point.

Angulus sterni