Sternal Angle of Louis

angulus sterni Ludovici

The sternal angle (angle of Louis, manubriosternal junction) is the palpable transverse ridge on the anterior sternum at the junction of the manubrium and the sternal body, corresponding to the level of the T4-T5 intervertebral disc. It is one of the most clinically important surface landmarks, marking the level of the aortic arch, the bifurcation of the trachea (carina), the second costal cartilage and second rib, and the upper limit of the cardiac percussion area.

Region: Chest

Clinical Relevance

Clinical Notes

The sternal angle is the universal starting point for rib counting in clinical examination: the second rib articulates with the sternum at this level, and ribs are counted downward from here. It is the surface marking for auscultating the aortic valve (second right intercostal space) and pulmonary valve (second left intercostal space). In median sternotomy, the sternal angle serves as a reference for ensuring symmetric skin incision. It is visible as a transverse ridge and palpable even in obese patients.

Pathology

Common Injuries & Conditions

Sternal Angle Disruption in Sternal Fracture

Direct sternal trauma from steering wheel impact or CPR produces sternal fractures most commonly at the sternal angle, detectable as point tenderness and crepitus at the manubriosternal junction with posterior displacement on lateral chest radiograph, associated with myocardial contusion given the T4 cardiac level.