304 THE ARTICULATIONS 



(ii) The Cuneo-navicular Articulation 



Class. — Diarthrosis. Subdivision. — Arthrodia. 



The ligaments uniting the navicular with the three cuneiform bones are : — 



Dorsal. Plantar. 



Medial. 



The dorsal cuneo-navicular ligament is very strong, and stretches as a continuous structure 

 on the dorsal surface of the navicular, between the tubercle of the navicular on the medial side, 

 and the dorsal cuboideo-navicular ligament laterally, passing forward and a little laterally to 

 the dorsal surfaces of the three cuneiform bones. 



The medial cuneo-navicular ligament is a very strong thick band which connects the tuber- 

 cle of the navicular with the medial surface of the first cuneiform bone. It is continuous 

 with the dorsal and plantar ligaments. Its lower border touches the tendon of the tibialis 

 posterior. 



The plantar cuneo-navicular ligament forms, like the dorsal, a continuous structure ex- 

 tending between the plantar surfaces of the bones. Its fibres pass forward and laterally. It 

 is in relation below with the tendon of the tibialis posterior. 



It must be noticed that the expanded tendon of insertion of the tibialis posterior, and the 

 ligaments uniting the navicular with the cuboid and cuneiform bones, pass forward and later- 

 aUy, while the peroneus longus tendon and the ligaments uniting the first and second rows of 

 bones, except the medial half of the dorsal talo-navicular ligaments, pass forward and medially. 

 This arrangement is admirably adapted to preserve the arches of the foot, and especially the 

 transverse arch. Had these tendons and ligaments run directly forward, all the strain on the 

 transverse arch would have fallen on the interosseous ligaments, but as it is, the arch is braced 

 up by the above-mentioned structures. 



(iii) The Intercuneiform and (iv) The Cuneo-cuboid Articulations 



Class. — Diarthrosis. Subdivision — Arthrodia. 



The uniting ligaments of these bones are divided into three sets : — 



Dorsal. Plantar. 



Interosseous. 



The dorsal ligaments are three in number, two, the dorsal intercuneiform, connecting the 

 three cuneiform bones, and a third, the dorsal cuneo-cuboid, uniting the third cuneiform with 

 the cuboid. They pass between the contiguous margins of the bones, and are blended behind 

 with the dorsal ligaments of the cuboideo-navicular and cuneo-navicular joints. 



The plantar ligaments are two in number: a very strong one, the plantar intercuneiform, 

 passes laterally and forward from the lateral side of the base of the first cuneiform to the apex 

 of the second cuneiform, winding somewhat to its lateral side. The second, the plantar cuneo- 

 cuboid, connects the apex of the third cuneiform with the anterior half of the medial surface of 

 the cuboid along its plantar border, joining with the plantar cuboideo-navicular ligament 

 behind. 



The interosseous ligaments are three in number. They are strong and deep masses of 

 ligamentous tissue which connect the second cuneiform with the first and third cuneiform bones, 

 and the third cuneiform with the cuboid; occupying all the non-articular portions of the apposed 

 surfaces of the bones. The ligaments extend the whole vertical depth between the second cunei- 

 form and the third, and the third cuneiform and the cuboid, and blend with the dorsal and 

 plantar ligaments; they are situated in front of the articular facets, and completely shut off 

 the synovial cavity behind from that in front. The ligament between the first and second cunei- 

 form bones occupies the inferior and anterior two-thirds of the apposed surfaces, and does not 

 generally extend high enough to separate the synovial cavity of the anterior tarsal joint from that 

 of the second and tliird metatarsal and cuneiform bones. If it does extend to the dorsal sur- 

 face, it divides the facets completely from one another, making a seventh synovial sac in the 

 foot. 



The synovial cavity will be described later on. 



The arterial supply i.s from the metatarsal and plantar arteries. 



The nerves are derived from the deep peroneal and medial and lateral plantar. 

 The movement permitted in these joints is very limited, and exists only for the purpose of 

 adding to the general pliancy and elasticity of the tarsus without allowing any sensible 

 alteration in the position of the dilTorcnt parts of the foot, as the medio-tarsal and talo-cal- 

 caneal joints do. It is simply a gliding motion, and either deepens or widens the transverse 

 arch. The third cuneiform being wedged in between the others is less movable, and so forms 

 a pivot upon which the rest can move. The movement is more produced by the weight of 

 the body than by direct mu.scular action; and of the muscles attached to this part of the 

 tarsus, all deepen the arch save the tibialis anterior, which pulls the first cuneiform up, and 

 so tends to widen it. 



