284 



THE ARTICULATIONS. 



The Anterior Ligament (Fig. 189) is a broad, thin, membranous layer, attached, 

 above, to the anterior margin of the lower extremity of the tibia ; below, to the 

 margin of the astragalus, in front of its articular surface. It is in relation, in front, 

 with the Extensor tendons of the toes, with the tendons of the Tibialis anticus and 

 Peroneus tertius, and the anterior tibial vessels and nerve ; behind, it lies in con- 

 tact with the synovial membrane. 



The Posterior Ligament is very thin, and consists principally of transverse 

 fibres. It is attached, above, to the margin of the articular surface of the tibia, 

 blending with the transverse tibio-fibular ligament ; below, to the astragalus, behind 

 its superior articular facet. Externally, where a somewhat thickened band of 

 transverse fibres is attached to the hollow on the inner surface of the external 

 malleolus, it is thicker than internally. 



The Internal Lateral or Deltoid Ligament is a strong, flat, triangular band,, 

 attached, above, to the apex and anterior and posterior borders of the inner mal- 

 leolus. The most anterior fibres pass forward to be inserted into the navicular 

 bone and the inferior calcaneo-navicular ligament ; the middle descend almost 

 perpendicularly to be inserted into the sustentaculum tali of the os calcis ; and the 

 posterior fibres pass backward and outward to be attached to the inner side of the 

 astragalus. This ligament is covered by the tendons of the Tibialis posticus and 

 Flexor longus digitorum muscles. 



Inferior tibio-fibular articulation. 



Ankle-joint. 



Tarsal articulations. 



FIG. 190. Ankle-joint : tarsal and tarso-metatarsal articulations. External view. Right side. 



The External Lateral Ligament (Fig. 190) consists of three distinctly special- 

 ized fasciculi of the capsule, taking different directions and separated by distinct 

 intervals ; for which reason it is described by some anatomists as three distinct 

 ligaments. 1 



The anterior fasciculus (anterior astragal o-fibular), the shortest of the three, 

 passes from the anterior margin of the external malleolus forward and inward to 

 the astragalus, in front of its external articular facet. 



The posterior fasciculus (posterior astragalo-fibular), the most deeply seated, 

 passes inward from the depression at the inner and back part of the external mal- 

 leolus to a prominent tubercle on the posterior surface of the astragalus. Its fibres 

 are almost horizontal in direction. 



1 Humphry, On the Skeleton, p. 559. 



