ANKLE JOINT. 



135 



somewhat below the margin of the bones, and serve to deepen the 

 cavity of articulation for the astragalus. 



The transverse ligament (fig. 64. 3) is a narrow band of ligamen- 

 tous 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 reflected upwards for a short distance between the 

 two bones. 



Actions. An obscure movement exists between the tibia and 

 fibula, which is principally calculated to enable the latter to resist 

 injury by yielding for a trifling extent to the pressure exerted. 



4. Ankle joint. The ankle is a ginglymoid articulation, the sur- 

 faces entering into the formation of the joint are the under surface 

 of the tibia with its malleolus and the malleolus of the fibula, above; 

 and the surface of the astragalus 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 sur- 

 face. It is in relation, in front, with the extensor tendons of the 



Fig. 62.* 



Fig. 63.t 



great and lesser toes, with the tendon of the tibialis anticus and pero- 

 neus tertius, and with the anterior tibial vessels and nerve. Pos- 

 teriorly it lies in contact with the extra-synovial adipose tissue and 

 with the synovial membrane. 



The internal lateral ligament or deltoid, is a triangular layer of 



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

 Part of the astragalus ; the rest is concealed by the ligaments. 3. The os calcis. 4. 

 The scaphoid bone. 5. The internal cuneiform bone. 6. The internal lateral or del- 

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

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



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

 the fibula. 3, 3. The astragalus. 4. The os calcis. 5. The cuboid bone. 6. The an- 

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

 middle fasciculus, attached to the os calcis. 8. Its posterior fasciculus, attached to the 

 astragalus. 9. The anterior ligament of the ankle. 



m 



