Fig. 197. Frontal Section through the (Right) Ankle-joint. 



Frozen Section. As the section did not pass directly t/irotigh the tip of the 

 External Malleolus some tissue was removed in order to expose this prominence. 



The Tibia and Fibula by means of their Malleoli form a socket which 

 grips the Astragalus. The External Malleolus extends to a lower level than the 

 Internal ; the joint cavity extends upwards between the lower ends of these bones 

 forming a recess caUed the Inferior Tibio-Fibular Articulation. To the Tibia and 

 Astragalus the Capsule is attached along the border of the articular cartilages 

 (on the anterior surface only does the Capsule extend to the neck of the 

 Astragalus). By this arrangement a considerable portion of the Neck of the 

 Astragalus may enter the joint cavity in extreme dorsi-flexion of the foot. Cor- 

 responding to the free movements in Dorsal and Plantar Flexion, the capsule is 

 loose in front and behind, so as to form folds (vide Fig. 199) but on either side 

 strong tense ligaments attach the Malleoli to the Astragalus and Os Calcis: the 

 Deltoid Ligament extending from the Internal Malleolus to the Astragalus and 

 Sustentaculum Tali, the Anterior and Posterior Astragalo-Fibular Ligaments and 

 the Calcaneo-Fibular Ligaments extending from the External Malleolus to the 

 Astragalus and Os Calcis respectively. 



The ankle-joint is therefore not easily accessible from the side; behind, it 

 lies at a considerable depth under the Tendo Achillis, but can be reached (cf. 

 Fig. 190). Its anterior aspect, on either side of the Extensor Tendons, is the i^ost 

 accessible (cf. Fig. 193). 



This figure also shews the position of the Peroneal Muscles enveloped in 

 their sheaths below the Outer Malleolus and the position of the Flexors on the 

 inner side. The Posterior Tibial Artery and Nerve have already divided into 

 Internal and External Plantar Branches which are now lying in a well-protected 

 position between muscles. Between the Astragalus and the Os Calcis, the Posterior 

 Calcaneo-Astragaloid Articulation can be seen ; this lies at a slightly higher level 

 than the tip of the External Malleolus. 



The Anterior Calcaneo-Astragaloid Joint which is separated from the 

 Posterior by the Interosseus Ligament (v. Fig. 199) is not an independent joint 

 but is a part of the Astragalo-Scaphoid Articulation, whereas the Posterior Calcaneo- 

 Astragaloid Articulation is quite independent and liable to independent affections. 

 If swollen it bulges forwards and outwards to point anteriorly at the Tip of the 

 External Malleolus. 



The movements of Abduction and Adduction are limited at this joint. 



The inner border of the foot is arched and does not touch the ground. 



