164 ANKLE JOINT. 



contact. This articulation is so firm that the fibula is likely to be broken 

 in the attempt to rupture the ligament. 



The anterior inferior ligament is a broad band, consisting of two fasci 

 culi of parallel fibres which pass obliquely across the anterior aspect of 

 the articulation of the two bones at their inferior extremity, from the tibia 

 to the fibula. 



The posterior inferior ligament (fig. 98, 2) is a similar band upon lh 

 posterior surface of the articulation. Both ligaments project somewha 

 below the margin of the bones, and serve to deepen the cavity of articu 

 lation for the astragalus. 



The transverse ligament (fig. 98, 3) is a narrow band of ligamentous 

 fibres, continuous with the preceding, and passing transversely across the 

 back of the ankle joint between the two malleoli. 



The synovial membrane of the inferior tibio-fibular articulation, is a 

 duplicature of the synovial membrane of the ankle joint reflected upwards 

 for a short distance between the two bones. 



fictions. An obscure degree of movement exists between the tibia and 

 fibula, w r hich is principally calculated to enable the latter to resist injury, 

 by yielding for a trifling extent to the pressure exerted. 



4. Anlde joint. The ankle is a ginglymoid articulation ; the surfaces 

 entering into its formation are the under surface of the tibia with its mal- 

 leolus and the malleolus of the fibula, above, and the surface of the astra- 

 galus with its two lateral facets, below. The ligaments are three in 

 number : 



Anterior, Internal lateral, External lateral. 



The anterior ligament is a thin membranous layer, passing from the 

 margin of the tibia to the astragalus in front of the articular surface. It 

 is in relation, in front, w r ith the extensor tendons of the great and lesser 

 toes, with the tendons of the tibialis anticus and peroneus tertius, and with 

 the anterior tibial vessels and nerve. Posteriorly it lies in contact with 

 (he extra-synovial adipose tissue and with the synovial membrane. 



Fig. 96 * Fig. 97.-J- 



* An internal view of the ankle joint. 1. The internal malleolus of the tibia. 2, 2 

 Pa^t of the astragalus : the rest is concealed by the ligaments. 3. The os calcis. 4. The 

 fccaphoid bone. 5. The internal cuneiform bone. 6. The internal lateral or deltoid 

 ligament. 7. The anterior ligament. 8. The tendo Achillis ; a small bursa is seen 

 interposed between the tendon and the tuberosity of the os calcis. 



f An external view of the ankle-joint. 1. The tibia. 2. The external malleolus of 

 '.he fibula. 3, 3. The astragalus. 4. The os calcis. 5. The cuboid bone. 6. The ante- 

 rior fasciculus of the external lateral ligament attached to the astragalus. 7. Its middle 

 lasnioulus, attached to the os calcis. 8. Its posterior fasciculus, attached to the astra 

 gains Q . The anterior ligament of the ankle. 



