Overview

Each of the twelve costal cartilages continues the anterior end of a rib at a costochondral joint (a primary cartilaginous joint without movement). The cartilages of ribs 1–7 articulate directly with the sternum: the first by a synchondrosis (immovable), the 2nd–7th by small synovial sternocostal joints. The cartilages of ribs 8–10 each articulate with the cartilage above by interchondral (synovial) joints, forming the costal margin (arch). The cartilages of 11 and 12 are short tips embedded in the abdominal musculature.

Costal cartilages increase in length from the 1st to the 7th and then decrease. Their flexibility allows the thorax to expand during inspiration and to absorb blows. With age they progressively calcify (often visible on chest radiographs), making the chest wall more rigid.

Location: Anterior thoracic wall, between the anterior ends of the ribs and the sternum/costal margin.

Anatomy

Histology: Hyaline cartilage with perichondrium; calcifies with age.

Function

Connect ribs to the sternum and each other
Give elasticity to the thoracic wall for breathing and impact absorption
Form the costal margins

Clinical significance

Costochondritis and Tietze syndrome

Inflammation of the costochondral or sternocostal joints causing reproducible chest-wall tenderness (a diagnosis of exclusion after cardiac causes); Tietze syndrome includes visible swelling, typically of the 2nd–3rd cartilages.

Rachitic rosary

Enlargement of costochondral junctions due to unmineralised osteoid in rickets (scurvy produces a sharper "scorbutic rosary").

Test yourself

The sternal angle (of Louis) is a key landmark because it lies at the level of:

The 1st costal cartilage and T2
The 4th costal cartilage and T6
The xiphisternal joint and T9
The 2nd costal cartilage and the T4–T5 intervertebral disc

Answer: The 2nd costal cartilage and the T4–T5 intervertebral disc

The manubriosternal joint lies opposite the 2nd costal cartilage (used to count ribs) and the T4–T5 disc. This plane marks the start and end of the aortic arch, the tracheal bifurcation, the pulmonary trunk bifurcation and the superior/inferior mediastinum boundary.