The radiate sternocostal ligaments 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.
They are composed of fasciculi which pass in different directions. The superior fasciculi ascend obliquely, the inferior fasciculi descend obliquely, and the middle fasciculi run horizontally. The superficial fibers are the longest; they intermingle with the fibers of the ligaments above and below them, with those of the opposite side, and in front with the tendinous fibers of origin of the Pectoralis major, forming a thick fibrous membrane (membrana sterni) which envelopes the sternum. This is more distinct at the lower than at the upper part of the bone.