Surface anatomy

Anteriorly, the first rib cannot be palpated below the clavicle, but the first intercostal space may be felt above the second rib. The position of the second rib is a reliable landmark anteriorly for determining the position of other ribs:

• palpate down the manubrium to the manubrio-sternal junction
• a ridge, the sternal angle, is palpable at this point as fat does not tend to accumulate in this area
• palpate laterally; almost invariably, the second costal cartilage is felt with the second rib in continuity
• other ribs can be located by counting inferiorly from the second rib

The lowest rib on each side to articulate with the sternum is usually the seventh. The costal margin on each side can be traced inferiorly to its anterolateral continuity with the tenth rib.

Posteriorly, the ribs may be located by counting upwards from the most inferior (12th) rib. If it is absent, rudimentary or short and hidden within the erector spinae muscles, the 12th rib may prove difficult to find. In the anatomical position, the inferior angle of the scapula lies at the level of the seventh rib.