Intra articular ligament of head of rib

The intra-articular ligament of head of rib (interarticular in older texts) is situated in the interior of the articulation of head of rib.

It consists of a short band of fibers, flattened from above downward, attached by one extremity to the crest separating the two articular facets on the head of the rib, and by the other to the intervertebral fibrocartilage; it divides the joint into two cavities.

In the joints of the first, tenth, eleventh, and twelfth ribs, the interarticular ligament does not exist; consequently, there is only one cavity in each of these articulations.

This ligament is the homologue of the ligamentum conjugale present in some mammals, and uniting the heads of opposite ribs, across the back of the intervertebral fibrocartilage.