228 



ARTICULATIONS. 



Actions. The movement permitted in these articulations is limited to a very 

 slight gliding of the articular surfaces one upon another. 



4. ANKLE-JOINT. 



The Ankle is a ginglymoid or hinge-joint. The bones entering into its forma- 

 tion are the lower extremity of the tibia and its malleolus, and the malleolus of 

 the fibula, above, which, united, form an arch, in which is received the upper 

 convex surface of the astragalus and its two lateral facets. These surfaces are 

 covered with cartilage, and connected together by the following ligaments : 



Anterior. Internal Lateral. 



External Lateral. 



The Anterior Ligament (fig. 143) is a broad, thin, membranous layer, attached 

 above, to the margin of the articular surface of the tibia ; below, to the margin of 



Fig. 143. Ankle-joint : Tarsal and Tarso-metatarsal Articulations. Internal View. Right Side. 



TASSO-MCTATARS 

 ARTIC ?! 



TARSAL ARTIC"? 



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

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

 tertius, and the anterior tibial vessels and nerve ; behind, it lies in contact with 

 the synovial membrane. 



The Internal Lateral or Deltoid Ligament consists of two layers, superficial 

 and deep. The superficial layer is a strong, flat, triangular band, attached, above, 

 to the apex and anterior and posterior borders of the inner malleolus. The most 

 anterior fibres pass forwards to be inserted into the scaphoid ; the middle descend 

 almost perpendicularly to be inserted into the os calcis ; and the posterior fibres 

 pass backwards and outwards to be attached to the inner side of the astragalus. 

 The deep layer consists of a short, thick, and strong fasciculus which passes 

 from the apex of the malleolus to the inner surface of the astragalus, below the 

 articular surface. This ligament is covered in by the tendons of the Tibialis 

 posticus and Flexor longus digitorum muscles. 



The External Lateral Ligament (fig. 144) consists of three fasciculi, taking 

 different directions, and separated by distinct intervals. 





