The =articular surface= (Facies articularis) faces upward and backward, and is chiefly adapted to the distal surface of the second phalanx, but a narrow flattened area along the posterior border articulates with the third sesamoid. The =anterior= or =coronary border= forms a central eminence, the =extensor= (or pyramidal) =process= (Processus extensorius), to the front of which the anterior extensor tendon is attached. On either side is a depression for the attachment of the lateral ligament. The =dorsal= or =wall surface= (Facies dorsalis) slopes downward and forward. The angle of inclination on the ground plane is about 45 to 50 degrees in front. Laterally the height diminishes, and the slope becomes steeper, especially on the inner side. From side to side the curvature is almost semicircular. The surface is rough and porous, resembling pumice stone somewhat. It is perforated by numerous foramina of various sizes; a series of larger ones is situated on or near the lower border. On either side the =dorsal= (or preplantar) =groove= (Sulcus dorsalis) passes forward from the wing and ends at one of the larger foramina. In the fresh state this surface is covered by the matrix of the wall of the hoof. The =inferior= or =distal border= is thin, sharp, and irregularly notched; there is commonly a wider notch in front. The =volar= or =inferior surface= (Facies volaris) is arched, and divided into two unequal parts by a curved rough line, the =semilunar crest= (Crista semilunaris). The larger anterior area is crescent-shaped, concave, and comparatively smooth; it corresponds to the sole of the hoof, and may be termed the =sole surface=. The posterior part is much smaller, and is semilunar; it is related to the deep flexor tendon, and is hence called the =flexor= or =tendon surface= (Facies flexoria). It presents a central prominent rough area, on either side of which is the =volar= (or plantar) =foramen= (Foramen volare), to which the =volar= (or plantar) =groove= (Sulcus volaris) conducts from the wing. The foramina lead into the =semilunar canal= within the bone, from which small canals lead to some of the foramina of the wall surface. The deep flexor tendon is inserted into the semilunar crest and the central rough area behind it. The volar grooves and foramina transmit the terminations of the digital arteries into the semilunar canal, where they meet and form a terminal arch, from which branches pass through canals in the bone and emerge through the foramina on the wall surface. The =angles= or =wings= (Anguli) are prismatic masses which project backward on either side; the inner one is usually the shorter. Each is divided into upper and lower parts by a notch, or is perforated by a foramen which leads to the vascular groove on the side of the wall surface.[25] The upper border carries the lateral cartilage.