The first through seventh ribs have a direct anterior atachment to the sternum (by cartilage) and these ribs are called true ribs (vertebrosternal ribs)
- articulations of the cartilages of the true ribs with the sternum are arthrodial joints, with the exception of the first, in which the cartilage is directly united with the sternum, and which is, therefore, a synarthrodial articulation
- ligaments connecting them are:
- Articular Capsules - capsules surround the joints between the cartilages of the true ribs and the sternum
- Interarticular Sternocostal - consist of broad and thin membranous bands that radiate from the front and back of the sternal ends of the cartilages of the true ribs to the anterior and posterior surfaces of the sternum
- Radiate Sternocostal - only found constantly between the second costal cartilages and the sternum
- the second rib is connected with the sternum by means of an interarticular ligament, attached by one end to the cartilage of the rib, and by the other to the fibrocartilage which unites the manubrium and body of the sternum
- occasionally the cartilage of the third rib is also connected with the first and second pieces of the body of the sternum by an interarticular ligament.
- more rarely, similar ligaments are found in the other true ribs (four, five, six, seven)
- Costoxiphoid - these are ligaments that connect the anterior and posterior surfaces of the seventh costal cartilage, and sometimes those of the sixth, to the front and back of the xiphoid process
The remaining five pairs of ribs are called false ribs because their costal cartilages do not attach directly to the sternum. The cartilages of the eighth, ninth and tenth ribs attach to each other and then to the cartilage of the seventh rib. These false ribs are also known as vertebrochondral ribs.
The eleventh and twelfth false ribs are designated as floating (vertebral ribs) - this is because their anterior ends do not attach even indirectly to the sternum. They attach only posteriorly to the thoracic vertebrae.