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Posterior ribs

Posterior ribs are the backward portions of each rib located closest to the spine, where the ribs originate and articulate with the thoracic vertebrae (costovertebral joints). Anatomically, this refers to the rib segments that extend from the vertebral column around the back and posterolateral chest wall before curving toward the sides. On a chest X-ray, posterior ribs usually appear more horizontal, more prominent, and more clearly defined as they cross the lung fields. Because they are easier to see and count, clinicians often use the posterior ribs to assess the degree of inspiration (how deep a breath was taken) and to help localize abnormalities or suspected rib injuries along the back portion of the rib cage.

Posterior ribs — X-ray appearance (PA chest X-ray)

  • Start near the spine and run across the back of the chest

  • Look more horizontal

  • Usually more prominent / clearer / sharper than anterior ribs

  • Easier to identify and count (commonly used for assessing inspiration)

  • Form distinct repeating arches across the lung fields