The bones concerned in the construction of this joint are the os coronae or coronet-bone, the os pedis or foot-bone, and the os naviculare or navicular bone. The two last-named bones are united together in such a manner as to form two concavities separated by a slight central ridge, to which are applied the two convexities and central groove upon the lower end of the coronet-bone.
The ligaments of this joint are: 1, The capsular, common to the three bones. 2. The lateral ligaments uniting the os coronae to the foot-bone. 3. The navicular ligaments: a, the broad or interosseous ligament extending from the anterior border of the navicular bone to the under surface of the os pedis or foot-bone; b, the lateral navicular ligaments which proceed from each extremity of the navicular bone (l) to the wing of the foot-bone, (2) to the inner surface of the lateral cartilage, and (3) to the side of the coronet-bone.
Fig. 357. - Ligaments of the Pastern and Foot.
A, Posterior aspect, outer layer. B, Inner layer. c, Side view.
1, Superior sesamoid or suspensory ligament, giving off a band, 2, to the extensor pedis. 3, Lateral sesamoid ligament. 4, Superficial inferior sesamoid ligament. 5, Deep sesamoid ligament. 6, Crucial ligament. 7, Lateral ligament of the coronet-joint. 8, Posterior interphalangial ligament. 9, Inter-sesamoidal substance over which the tendons pass. 10, Sesamoid bones. 11, Ligamentous substance common to the coronal and navicular bones. 12, Navicular bone. 13, Intersesamoid ligament. 14, Lateral navicular ligament. 15, Anterior lateral ligament of the coffin-joint.
The movements of the coffin-joint are flexion and extension.