The sternal angle is an important bony anatomical landmark, located on the sternum, where the sternal stalk and the sternal body join. Under normal conditions, the sternal angle is defined when a distinctly elevated bone is palpated downward from the suprasternal notch, the uppermost part of the sternum. The ends of the sternal angle are flat against the second rib cartilage, so the sternal angle is an important landmark for counting ribs. In addition, the sternal angle is flat against the lower edge of the fourth thoracic vertebra or the fourth and fifth thoracic vertebral spaces, so clinically the sternal angle is also a marker for counting vertebrae. The sternal angle plane is also an important plain view of the chest. The sternal angle is the interface between the upper and lower mediastinum, and the back flat against the beginning and end of the aortic arch.