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Costal notches

The costal notches are a series of indentations along the lateral borders of the sternum where the costal cartilages of the ribs articulate with the sternum. They are present on the manubrium, body, and xiphoid process of the sternum. The first costal notch articulates with the first rib cartilage at the manubrium, while the second costal notch lies at the manubriosternal junction (sternal angle). Subsequent costal notches on the sternum’s body accommodate the third through seventh costal cartilages. These notches form the sternocostal joints, which are primarily cartilaginous or synovial depending on the rib level, and they play an important role in the flexibility and mechanics of the thoracic cage.

Synonyms

  • Sternocostal notches

  • Sternal costal facets

  • Costal cartilage articulations

Function

  • Provide articulation sites for the costal cartilages of the ribs

  • Maintain stability and flexibility of the thoracic cage

  • Allow for respiratory movements by accommodating rib elevation and depression

  • Serve as landmarks for thoracic imaging and surgical approaches

MRI Appearance

T1-weighted images:

  • Costal notches appear as low-signal cortical bone indentations along the sternum

  • Adjacent costal cartilage shows intermediate to low signal

  • Surrounded by hyperintense marrow and soft tissue for contrast

T2-weighted images:

  • Cortical bone remains hypointense

  • Costal cartilage demonstrates intermediate signal 

  • Useful for detecting inflammation, degeneration, or joint effusion at the sternocostal joints

STIR (Short Tau Inversion Recovery):

  • Suppresses fat, highlighting edema, inflammation, or traumatic injury at the sternocostal joints

  • Pathological changes (costochondritis, fracture, arthritis) appear hyperintense compared to normal cartilage

T1 Post-Contrast (Gadolinium-enhanced):

  • Normal costal notches and cartilage show mild to no enhancement

  • Inflamed or pathological regions demonstrate heterogeneous or rim enhancement

  • Helpful for identifying infection, arthritis, or neoplastic infiltration

CT Appearance

Non-contrast CT:

  • Costal notches appear as bony depressions on the sternum’s lateral borders

  • Costal cartilage is seen as soft tissue density extending from the ribs to the notches

  • Calcification of costal cartilage may be seen with age

Contrast-enhanced CT (CECT):

  • Clearly shows the sternocostal joints and relationships with adjacent mediastinal structures

  • Useful in detecting fractures, arthropathy, inflammatory changes, or tumors involving sternum and costal cartilage

MRI image

Costal notches anatomy MRI CORONAL image -img-00000-00000

CT images

Costal notches anatomy CT axial image -img-00000-00000

CT images

Costal notches anatomy CT coronal image -img-00000-00000