THE ANKLE-JOINT. 377 



of the leg, and the integument ; behind, with the inferior inter-osseous ligament ; 

 and lies in contact with the cartilage covering the astragalus. 



The Posterior Inferior Ligament, smaller than the preceding, is disposed in a 

 similar manner on the posterior surface of the articulation. 



The Transverse Ligament is a long, narrow band, continuous with the preceding, 

 passing transversely across the back of the joint, from the external malleolus to 

 the posterior border of the articular surface of the tibia, almost as far as its mal- 

 leolar process. This ligament projects below the margin of the bones, and forms 

 part of the articulating surface for the astragalus. 



The Inferior Interosseous Ligament consists of numerous short, strong, fibrous 

 bands which pass between the contiguous rough surfaces of the tibia and fibula, 

 and constitute the chief bond of union between the bones. This ligament is con- 

 tinuous above with the interosseous membrane. 



The Synovial Membrane lining the articular surface is derived from that of the 

 ankle-joint. 



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

 slight gliding of the articular surfaces one upon another. 



IV. Ankle-joint. 



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

 tion are the lower extremity of the tibia and its malleolus and the external mal- 

 leolus of the fibula. These bones are united above, and form a mortise to receive 

 the upper convex surface of the astragalus and its two lateral facets. The bony 

 surfaces are covered with cartilage, and connected together by a capsule, which in 

 places forms thickened bands constituting the following ligaments : 



Anterior. Internal Lateral. 



Posterior. External Lateral. 



The Anterior Tibio-tarsal Ligament (Fig. 263) is a broad, thin, membranous 

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



Tarso- metata rsal 

 articulations. 



^^B^' 



FIG. 263. Ankle-joint : tarsal and tarso-metatarsal articulations. Internal view. Right side. 



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 



