THE ANKLE-JOINT. 



283 



The Anterior Inferior Ligament (Fig. 190) is a flat, triangular band of fibres, 

 broader below than above, which extends obliquely downward and outward 

 between the adjacent margins of the tibia and fibula, on the front aspect of the 

 articulation. It is in relation, in front, with the Peroneus tertius, the aponeurosis 

 of the leg, and the integument; behind, with the inferior interosseous ligament; 

 and lies in contact Avith 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 or Inferior Ligament lies under cover of the posterior 

 ligament, and is a strong, thick band of yellowish fibres which passes 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 malleolar process. This liga- 

 ment 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, which forms a mortise to receive the upper convex surface of 

 the astragalus and its two lateral facets. The bony surfaces are covered with carti- 



Tarso-metata 

 articulations 



Tarsal articulations 



FIG. 189. Ankle-joint : tarsal and tarso-metatarsal articulations. Internal view. Right side. 



lage and connected together by a capsule, which in places forms thickened bands 

 constituting the following ligaments: 



Anterior. Internal Lateral. 



Posterior. External Lateral. 



