ANKLE JOINT. 



153 



The inferior interosseotis ligament consists of short and strong 

 fibres, which hold the bones firmly together inferiorly, where they are 

 nearly in 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 

 fasciculi 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. 75, 2) is a similar band upon 

 the posterior surface of the articulation. Both ligaments project some- 

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

 articulation for the astragalus. 



The transverse ligament (fig. 75, 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 of the synovial membrane of the ankle joint reflected up- 

 wards for a short distance between the two bones. 



Actions. An obscure degree of 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. A nkle-joint. The ankle is a ginglymoid articulation ; the surfaces 

 entering into its formation 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 surface. It 

 is in relation, in front, with the ex- 

 tensor tendons of the great and les- 

 ser 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 the extra-synovial adi- 

 pose tissue and with the synovial 

 membrane. 



Fig. 73.* 



* 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 deltoid ligament. /. The anterior ligament. 8. The 

 tendo Achillis ; a small bursa is seen interposed between this tendon and the 

 tuberosity of the os calcis. 



