Tarso-metatarsal articalations.—The plane surface on the wedge-shaped tarsal extremity of each metatarsal bone is applied to correspond ing plane surfaces on the cuneiform bones and the cuboid. The first, second, and third meta tarsal bones, counting from within outwards, are articulated with the first, second, and third cuneiforms, and the fourth and fifth with the cuboid; the second metatarsal, however, is additionally articulated with the first and third cuneiforms, by its lateral surfaces being, as it were, mortised into a cavity formed by these three bones, and each of the other metatarsal bones is articulated with its fellow on each side of it. These articulations have the following common characters : they are planiform arthro di, each articular surface is covered by a thin layer of cartilage, and they all have ligaments similarly arranged in two sets, dorsal and plantar.
The first tarso-metatarsal articulation has a greater extent of its articular surfaces than those of the others. its plantar ligament is of great strength and extends from the great cuneiform, directed obliquely forwards and outwards to the first metatarsal bone, continuous posteriorly with the cuneo-scaphoid ligament, and strength ened by fibres from the tendon of the tibialis posticus, and on the outside by fibres from the tendon of the peroneus longus. The dorsal ligament consists of short and parallel fibres ; its breadth is equal to that of the cuneiform bone ; it is a weak and membranous ligament. This articulation has a synovial membrane distinct from that of the other tarso-metatarsal joints.
The second tarso-metatarsal articulation is the most solid of all, from the fact of the pos terior extremity of the metatarsal hone being fitted into the mortise-shaped cavity formed by the cuneiform bones. Its ligaments, it may naturally be expected, are more complicated than those of the other joints of this row ; thus it has three dorsal ligaments, a middle one, possessing common characters with those of the other joints, proceeding directly from behind forwards from the second cuneiform to the second metatarsal bone; the others are ex tended, one from the internal cuneiform obliquely outwards to the second metatarsal, the other from the third cuneiform obliquely inwards to the same bone. We find, moreover, two plantar ligaments, one short and direct, passing from the second cuneiform bone to the second metatarsal, the other much longer and more oblique, coining from the first cuneiform.
Lastly, this articulation has an interasscous h‘ra mem, which is extended from the lateral facet on the external surface of the first cuneiform to a corresponding one on the internal surface of the second cuneiform.
Each of the remaining tarso-metatarsal arti culations has its dorsal ligaments, of which those of the third and fourth are direct, and that of the fifth is extended obliquely outwards from the cuboid to the fifth metatarsal bone. In all three, the place of plantar ligament is supplied by the sheath of the long peroneal tendon, and the fifth receives additional strength from fibres given off from the tendon of the peroneus brevis. In the third there is an interosseous ligament between the third and fourth metatarsal bones, and from the anterior part of the external surface of the third cunei form to the fourth metatarsal.
The five tarso-nietatarsal articulations have four synovial membranes amongst them : the first, as has already been mentioned, has a distinct one ; the second lines the contiguous surfaces of the first and second cuneiform bones, and is prolonged over the mortise-shaped cavity and the articular portions of the second meta tarsal. The third lines the articular portions of the third cuneiform and third metatarsal, and is prolonged on either side of the latter in the form of two culs-de-sac into the space between the latter bone and the second meta tarsal on the inside, and the fourth on the outside. In fine, the fourth synovial membrane is common to the fourth and fifth tarso-meta tarsal joints.
Metatarsal articulatians.—The four external metatarsal bones are articulated with each other by means of the contiguous articular facets on the lateral surfaces of their posterior extremi ties. They are maintained in apposition by inter-osseous ligaments which pass from one metatarsal bone to the other, being inserted ioto rough surfaces immediately above the articular portion of each bone. Moreover, these joints have dorsal and plantar ligaments, which consist of ligamentous fibres directed transversely from one bone to the other. The plantar ligaments are considerably stronger and thicker than the dorsal.
The anterior extremities of the five meta tarsal bones, although not articulated together by surfaces which play upon each other, are yet connected by a common transverse ligament which passes from one bone to the other, being attached to the plantar surface of each bone, and covered by the sheaths of the flexor ten dons.