Interchondral joints

Articular surfaces

Interchondral joints are articulations formed by the costal cartilages between the 6th and 7th, 7th and 8th, and 8th and 9th and 9th and 10th rib. Being synovial plane joints, the articulating surfaces of the costal cartilages 6-9 are covered with hyaline cartilage.

The articulating surfaces of the 9th and 10th costal cartilage are fibrous, meaning they are joined with dense fibrous connective tissue.

Ligaments and joint capsule

The joints formed by costal cartilages of ribs 6-9 are synovial plane joints enclosed by a fibrous capsule and lined by synovial membrane. The joint capsule is reinforced by lateral and medial interchondral ligaments. The joint formed between the 9th and 10th costal cartilage is not lined by synovial membrane and, in some cases, may be absent altogether.

Innervation

The interchondral joints are supplied by the adjacent intercostal nerves.

Blood supply

The interchondral joints are supplied by the adjacent anterior intercostal arteries.

Movements

The interchondral joints are plane-type joints, meaning they provide little to no movement. They only allow a slight gliding movement which aids the general mobility of the thoracic cage. This is especially pronounced during functions such as breathing, in which the gliding movements of the interchondral joints, together with movements of the costovertebral and costotransverse joints, allow elevation of the ribs.The interchondral joints specifically produce gliding movements in the lower ribs, allowing their elevation and increase of the transverse diameter
of the thorax.

The main muscles that act on these joints are the interchondral portions of the internal intercostal muscles. These muscles are accessory respiratory muscles; together with the external intercostal muscles, rotate the ribs superiorly at their posterior axes and thereby elevate the ribs and sternum.