Chondro-Sternal Articulations

Costo-Chondral Articulations

The costo-chondral junctions are synarthroses. The rib has a concave surface which receives the convex end of the cartilage. They are united by the continuity of the strong periosteum and perichondrium.

These joints (Articulationes sternocostales) are diarthroses formed by the junction of the cartilages of the sternal ribs with the sternum. The articular ends of the cartilages (except the first) are somewhat enlarged, and present surfaces of cylindrical curvature. The articular surfaces on the sternum for the first pair of cartilages are placed close together on the dorsal border of the cariniform cartilage (Manubrium sterni); the other seven are placed laterally at the junction of the segments. The capsules are strong and tight; the first pair of joints has a common capsule, and the cartilages articulate with each other medially. The lower ends of the first pair of ribs are firmly attached to each other by dense fibrous tissue, which is prolonged forward along the upper margin of the cariniform cartilage and is continuous behind with the sternal ligament. Each of the other capsules is reinforced dorsally by the superior costo-sternal ligament (Ligamentum sternocostale radiatum), composed of radiating fibers which blend with the sternal ligament. The movement is rotation around a nearly vertical axis, except in the case of the first pair of joints.