ANKLE-JOINT 



30t 



ceding, passing transversely across the back of the joint, from the external 

 malleolus to the tibia, a short distance from its malleolar process. This liga- 

 ment projects below the margin of the bones, and forms part of the articulating 

 surface for the astragalus. 



The Synovial Membrane lining the articular surfaces 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 malleolus 

 of the fibula. These bones are united above, and form an arch, 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 the following 

 ligaments : 



Anterior. Internal Lateral. 



External Lateral. 



The Anterior or Tibio-tarsal Ligament (Fig. 210) is a broad, thin, membranous 

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



Fig. 210. Ankle-joint : Tarsal and Tarso-metatarsal Articulations. 



Eight Side. 



Internal View. 



TARSO-MCTATAR5AL. 

 AftTIC ?f 



TARSAL ARTIC"? 



to the margin of the astragalus, in front of its articular surface. It is in rela- 

 tion, 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 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 



