costalcartilages

Costal cartilages are bars of hyaline cartilage that connect the anterior ends of the ribs to the sternum or to the costal cartilage above, forming the front portion of thethoracic cage. They extend from the first through the tenth ribs, contributing to the elasticity and resilience of the rib cage during breathing. Ribs 1–7 have costal cartilages that attach directly to the sternum (true ribs). Ribs 8–10 attach to the costal cartilage of the rib above (false ribs). Ribs 11 and 12 do not reach the sternum (floating ribs).

Structure and joints: Each costal cartilage consists of hyaline cartilage with a surrounding perichondrium. The costochondral joints, where the rib meets its cartilage, are primary cartilaginous joints (synchondroses) with limited movement. The cartilages then articulate with the sternum at the sternocostal joints; the first sternocostal joint is a synchondrosis, while the second through seventh sternocostal joints are typically synovial plane joints that allow small gliding movements during respiration.

Development and aging: Costal cartilages form by endochondral ossification from mesenchymal precursors in the thoracic wall. With aging, these cartilages may undergo calcification and partial ossification, which can be more conspicuous on imaging in older individuals.

Clinical relevance: Calcification of costal cartilages can affect radiographic interpretation. Inflammation of the costal cartilages, termed costochondritis, causes chest wall pain and tenderness. Trauma or degenerative changes can also affect the cartilages and the integrity of the anterior thoracic cage.