17i 



AETICULATIOXS OF THE LOWER LIMB. 



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 liga- 

 ment. 



The external lateral ligament consists of three distinct bands 

 se]iarated 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 forwards and inwards from the fore 

 part of the outer malleolus to a part of the astragalus in front of its 

 external malleolar surface ; it is the shortest of the three. 3. The 

 posterior l)and, the strongest of the three, passes almost horizontally 

 inwards from the pit on the inner and back part of the malleolus to the 

 posterior surface of the astragalus. 



Fig. 156. — Transverse-Vertical Section of the Eight 

 Ankle-.Joint near its IMiddle, and of the Posterior 

 Talo-Calcaneal Articulation, so as to show the 

 Shape op the Articular Surfaces and Cavities, 

 a'lewed frou before. (a. t.) | 



1, internal, 2, external malleolus ; 3, placed on the astra- 

 galus at tlie angle Ijetween its superior and its external 

 malleolar surfaces ; 4, interosseous tibio-fibular ligameut ; 

 5, internal lateral ligament of the ankle-joint ; 6, susten- 

 taciihun tali ; 7, calcaneo-fibular or middle part of the 

 external lateral ligament ; S, inner part of the interosseous 

 calcaneo-talar ligament ; 9, great tuberosity of the cal- 

 caneum : between the tibia, fibula and a.stragalus, the 

 synovial cavity is indicated by the dark space enclosed by a 

 white line ; between the astragalus and os calcis a sectioa 

 of the posterior calcaneo-talar synovial cavity is sho\\T3. 



The anterior and posterior ligaments are 



merely scattered fibres in front of and l^ehind 

 the joint ; those of the posterior ligament are weak and principally 

 transverse. 



The synovial membrane of the ankle-joint extends upwards by a 

 small process which lines the inferior peroneo-tibial articulation. 



IVCovements. — The movements of the ankle-joint are mainly those of flexion 

 and extension of the foot, the directions of those movements being- in-incipally 

 determined by the shape of the articnlar surfaces. The extei-nal border of the 

 superior cartilaginous sm-face of the astragalus is cui'ved. and longer than the 

 internal border, and hence extension of the ankle-joint is accompanied with a 

 slight inward movement of the toes. The horizontal surfaces of both the tibia 

 and astragalus are broader in front than behind : hence in complete extension of 

 the ankle the naiTOw part of the astragalus is brought into the widest part of 

 the space between the malleoli, and a certain amount of lateral motion is allowed, 

 whereas in complete flexion, as when the weight of the body, \fith. completely 

 bended knees, is supported on the toes, the broad part of the surface of the 

 astragalus is pushed back into the naiTOwest part of the space, and the inferior 

 extremity of the fibula is pressed upon, so as to stretch the ligaments between it 

 and the tibia, and thus to prevent lateral movement of the joint, and give it at 

 the same time a certain amount of spring. There apjiears to be no other move- 

 ment between the til)ia and fibula ; these bones being bound together at their 

 lower ends with remarkable firmness. 



ARTICULATIONS OP THE FOOT. 



ArticulatioinS of the Calcakeuji, Astragalus, akd Scaphoid 



