THE TARSAL JOINTS 



305 



(c) The Transverse Tarsal Joints 



The articulations of the anterior and posterior portions of the tarsus, although 

 in the same transverse line, consist of two separate joints, viz., (i) a medial, the 

 talo-navicular, which communicates w4th the anterior talo-calcaneal articulation; 

 and (ii) a lateral, the calcaneo-cuboid, which is complete in itself. The move- 

 ments of the anterior upon the posterior portions of the foot take place at these 

 joints simultaneously. It will be most convenient to deal with the joints sepa- 

 rately as regards the ligaments; while the arteries, nerves, and movements will 

 be considered together. 



(i) The Talo-navicular Articulation 



Class.^ — Diarthrosis. Subdivision. — Enarthrodia. 



This is the only ball-and-socket joint in the tarsus. It communicates with 

 the anterior talo-calcaneal articulation, and two of the ligaments which close it in 

 do not touch the talus, but pass from the calcaneus to the navicular. The uniting 

 ligaments include, in addition to the articular capsule, the following: — 



Lateral calcaneo-navicular. Plantar calcaneo-navicular 



Talo-navicular. 



The lateral calcaneo-navicular has been already described (p. 302). 



The plantar calcaneo-navicular ligament (figs. 335 and 336) is an exceedingly dense, thick 

 plate of fibro-elastic tissue. It extends from the sustentaculum tali and the under surface of 

 the calcaneus in front of a ridge curving laterally to the anterior tubercle of that bone, to the 



Fig. 335. — View of the Foot from above, vv^ith the Talus removed to show the Plantar 

 AND Lateral Calcaneo-navicular Ligaments 



Dorsal cuboideo-navicular ligament 



Dorsal calcaneo-cuboid ligament' 



Medial calcaneo-cuboid ligament 



Lateral calcaneo-navicular ligament' 



Cut edge of interosseous ligament 



Plantar calcaneo-navicular 

 ligament 

 YI J\ — Tendon of tibialis posterior 



whole width of the inferior surface of the navicular, and also to the medial surface of the navicular 

 behind the tubercle. Medially it is blended with the anterior portion of the deltoid ligament of 

 the ankle, and laterally with the lower border of the lateral calcaneo-navicular ligament. It 

 is thickest along the medial border. Its upper surface loses the well-marked fibrous appear- 

 ance which the ligament has in the sole, and becomes smooth and faceted. _ In contact 

 with the under surface of the ligament the tendon of the tibialis posterior pusses, giving consider- 

 able support to the head of the talus by assisting the power and protecting the spring of the 

 ligament. The fibres of the ligament run forward and medially. On account of its elasticity it 

 is sometimes termed the spring ligament. 



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