422 THE INFERIOR EXTREMITY 



The majority of the fibres of both the anterior and posterior 

 parts of the fibrous stratum of the capsule run transversely. 



The Lateral Accessory Bands (O.T. External Lateral 

 Ligament). The lateral accessory bands of the capsule of 

 the ankle joint are three in number, (i) The anterior talo- 

 fibular ligament; (2) the posterior talo-fibular ligament; 

 (3) the calcaneo-fibular ligament. 



The anterior talo-fibular ligament is the most anterior of 

 the three. It is a flattened band which passes forwards from 

 the anterior border of the lateral malleolus to the body of 

 the talus immediately adjacent to the fibular facet. 



The posterior talo-fibular ligament is the strongest and the 

 most posterior of the three bands. It runs almost horizon- 

 tally, from the deep pit posterior to the distal articular surface 

 of the fibula to a prominent tubercle on the posterior surface 

 of the talus. 



This tubercle is termed the posterior process of the talus. Generally 

 in the child, and sometimes in the adult, it is a separate piece of bone, 

 attached to the talus by a layer of cartilage and the surrounding 

 periosteum. In such cases it forms a supernumerary tarsal bone which 

 represents the os trigonuin found in some mammals. If this fact is not 

 kept in mind a fracture of the talus may be diagnosed when the separate 

 bone is seen in a radiograph of an injured ankle (Figs. 200, 201). 



The calcaneo-fibular ligament is a round, cord -like band 

 which passes from the distal end of the lateral malleolus to the 

 lateral surface of the calcaneus. 



Ligamentum Deltoideum (O.T. Internal Lateral Lig.). 

 The deltoid ligament is an accessory band on the medial 

 side of the joint. It is strong and of triangular form. Its 

 apex is attached to a shallow pit on the distal end of the 

 medial malleolus. Its fibres diverge from the apex, and are 

 attached in a continuous line, from before backwards, to the 

 navicular bone, the talus, sustentaculum tali of the calcaneus, 

 and posterior to that to the talus again. 



Stratum Synoviale. The synovial layer lines the internal 

 surface of the fibrous stratum of the capsule described above, 

 and in some cases it sends a small process proximally 

 between the tibia and fibula. It is thrown into a transverse 

 fold anteriorly when the joint is flexed, and into a similar 

 fold posteriorly when the joint is extended. 



Relations. Before the further examination of the joint 

 is proceeded with, replace the tendons, vessels, and nerves 



