FIG. 152.—LATERAL LIGAMENTS OF PASTERN JOINT AND SUSPENSORY LIGAMENTS OF NAVICULAR BONE. (After Schmaltz, Atlas d. Anat. d. Pferdes.) ] =Joint Capsule.=—This is attached around the margins of the articular surfaces. In front and laterally it is tight, and is blended with the extensor tendon and the lateral ligaments respectively. Posteriorly, it forms a considerable pouch which extends upward to about the middle of the second phalanx, where it is separated by a fibrous membrane from the digital synovial sheath. Laterally small pouches project outward (especially during volar flexion) against the lateral cartilages, just behind the lateral ligaments.[36] =Ligaments.=—The =lateral ligaments=, external and internal (Ligamentum collaterale ulnare, radiale), are short strong bands which are attached above in the depressions on either side of the lower part of the second phalanx, under cover of the lateral cartilage. They widen below and end in the depressions on either side of the extensor process and on the anterior end of the lateral cartilages. The =suspensory navicular ligaments=, external and internal (Ligamentum sesamoideum collaterale ulnare, radiale),[37] are strong, somewhat elastic bands, which form a sort of suspensory apparatus for the third sesamoid. They are attached superiorly in and above the depressions on either side of the distal end of the first phalanx and are here partly blended with the lateral ligaments of the pastern joint. They are directed obliquely downward and backward, and end chiefly on the ends and proximal border of the third sesamoid, but detach a branch to the inner surface of each lateral cartilage and wing of the third phalanx. The =inferior navicular ligament= (Ligamentum phalangeo-sesamoideum) reinforces the capsule interiorly. It is a strong layer of fibers which extend from the distal border of the third sesamoid to the tendon surface of the third phalanx, near the posterior margin of the articular surface. =Movements.=—The chief movements are flexion and extension. In the standing position the joint is extended. During volar flexion a very small amount of lateral movement and rotation can be produced by manipulation. Dorsal flexion is very limited. Dorsal flexion appears to be checked mainly by the deep flexor tendon, since in cases of rupture of the latter the toe turns up. The slight mobility of the posterior part of the socket for the second phalanx (formed by the third sesamoid) diminishes concussion when the weight comes on the foot. LIGAMENTS OF THE LATERAL CARTILAGES In addition to the bands mentioned above, which attach the lateral cartilages to the extremities of the navicular bone, there are three ligaments on either side which attach the cartilages to the phalanges. An ill-defined elastic band passes from the middle part of the border of the first phalanx to the upper part of the cartilage, detaching a branch to the plantar cushion.