THE ANKLE-JOINT. 



159 



The inferior extremities of the tibia and fibula are in contact by surfaces 

 which -for the most part are rough and bound together by ligament, but near 



Fig. 145. ARTICULATIONS OP THE KNEE, LEG AND ANKLE, SEEN Fi S- 145 - 



FROM BEFORE. | / , 



1, superior anterior tibio-fibular ligament ; 2, interosseous mem- 

 brane; 3, points to the anterior inferior tibio-fibular ligament; 4, 

 internal lateral ligament of the ankle-joint ; 5, middle vertical part 

 (calcaneo-fibular) of the external lateral ligament of the ankle-joint ; 

 6, anterior part (talo-fibular) of the same ; 7, anterior ligament of 

 the ankle-joint. 



their lower edges are smooth and covered by cartilage. The 

 tibial surface is concave, the fibular convex ; but the lower 

 edges of both surfaces are straight. The strong short 

 fibres which pass directly between the opposing surfaces 

 form the inferior interosseous ligament. The anterior liga- 

 ment is a flat band of fibres, extended obliquely over the 

 lower part of the bones, the direction of its fibres being 

 downwards from the tibia to the fibula. The posterior liga- 

 ment, somewhat triangular, is similarly disposed behind the 

 articulation ; its outer surface is covered by the peronei 

 muscles. The transverse ligament, longer and narrower 

 than the preceding, is placed immediately below it ; its 

 fibres are horizontal, and extend from the external 

 malleolus to the contiguous part and hinder border of the 

 articular surface of the tibia ; it closes the interval 

 between the bones. 



The synovial cavity lying between the small articular 

 surfaces is an extension of that of the ankle-joint. 



THE ANKLE-JOINT. In this articulation, which is a 

 hinge-joint, the inferior extremities of the tibia and 

 fibula, united so as to form a kind of arch, embrace 

 transversely the superior articular surface of the astragalus, 

 so as to render lateral movement impossible when the ligaments are tense. 



Fig. 146. 



Fig. 146. THE LOWER TIBIO-FIBULAR ARTICULATION AND 

 ANKLE-JOINT, FROM BEHIND. 



1, inferior posterior tibio-fibular ligament; 2, transverse 

 ligament ; 3, posterior fibres of the internal lateral ligament 

 of the ankle-joint ; 4, middle, and 5, posterior part of the 

 external lateral ligament of the aukle-joint ; 6, posterior 

 talo-calcaneal ligament. 



The internal lateral ligament is a flat fasciculus 

 of fibres, much broader at the lower than at the 

 upper part. One extremity is attached to the 

 inferior border of the internal malleolus; the other, 

 to the inner side of the astragalus, the os calcis, 

 and the scaphoid bone, as well as to the inferior 

 calcaneo-scaphoid ligament. 



The external lateral ligament consists of three distinct bands, separated by 

 intervals and disposed in different directions. 1. The middle band descends 

 from the extremity of the fibula, and is inserted into the middle of the 

 external surface of the os calcis. 2. The anterior band passes obliquely 



