352 



THE AETICULATIONS OR JOINTS. 



Anterior talo- 

 fibular ligament 

 Articular facet on N 



lateral malleolus 



Calcaneo-fibular 

 ligament 



Posterior ligament 

 of lateral malleolus 



Posterior talo-fibular 

 ligament 



Distal ligament of 

 lateral malleolus 



Synovial pad of fat 



of the lateral malleolus. This facet is situated immediately in front of the deep 

 pit which characterises the posterior part of this surface of the fibula. 



A small lunated facet is frequently found upon the anterior surface of the distal end of the 

 tibia, particularly among those races characterised by the adoption of the " squatting " posture. 

 When this facet exists it is continuous with the anterior margin of the roof of the socket, and it 

 articulates with a similar facet upon the superior surface of the neck of the talus in the 

 extreme flexion of the ankle-joint which "squatting" entails. 



The articular surface upon the body of the talus adapts itself to the tibio- 

 fibular socket, and presents articular facets corresponding to the roof and sides of 

 the socket. Thus the superior surface of the talus possesses a quadrilateral 

 articular area, wider in front than behind, distinctly convex in the antero-posterior 

 direction, and slightly concave transversely. In addition, towards its postero- 

 lateral margin, there is also a narrow antero-posterior facet corresponding to the 

 distal ligament of the lateral malleolus. The articular cartilage of this superior 

 surface is continued without interruption to the tibial and fibular sides of the bone, 

 although the margins of the superior area are sharply denned from the facets on 



the sides, the lateral of which 

 is triangular in outline, while 

 the medial is piriform, but 



in eacn case the surface is 

 vertical. 



Ligaments. The liga- 

 ments form a complete in- 

 vestment for the joint, i.e. 

 a fibrous stratum of an 

 articular capsule in which 

 the individual parts vary 

 considerably in strength, 

 and are described under 

 separate names. Their 

 proximal attachments are 



restricted to the epiphyses of the distal ends of the tibia and fibula, and the 

 epiphyseal lines are therefore extra-capsular. 



The anterior ligament is an extremely thin membrane, containing very few 

 longitudinal fibres. It extends from the distal border of the tibia to the 

 dorsal border of the head of the talus, passing in front of a pad of fat which 

 fills up the hollow above the neck of that bone. 



The posterior ligament is attached to contiguous non-articular borders of the tibia 

 and talus. Many of its fibres radiate medially from the lateral malleolus. This 

 aspect of the joint is strengthened by the strong, well-defined, distal ligament of the 

 lateral malleolus already described in connexion with the tibio-fibular syndesmosis. 

 The lateral ligament (Figs. 321, 322, and 324) is very powerful, and is divisible 

 into three fasciculi, which are distinguished from each other by names, descriptive 

 of their chief points of attachment. 



Lig. Talofibulare Anterius. The anterior fasciculus is the shortest. II 

 extends from the anterior border of the lateral malleolus to the talus immediately 

 in front of its lateral articular surface. 



Lig. Calcaneofibulare. The middle fasciculus is a strong and rounded core 

 It is attached by one end to the front of the tip of the lateral malleolus, and by 

 the other to the lateral side of the calcaneus immediately proximal and posterior 

 to the groove for the peroneal tendons. 



Lig. Talofibulare Posterius. The posterior fasciculus is the strongest. It 

 runs transversely between the distal part of the fossa on the medial aspect 

 of the fibular malleolus and the posterior surface of the talus, where it is attached 

 to the posterior process and the adjoining rough surface. Sometimes this process 

 is detached from the talus, and represents a separate bone the os trigonum. 



Lig. Deltoideum. The deltoid ligament is the medial ligament of the ankle-joint 

 (Figs. 322 and 323). It has the general shape of a delta, and is even stronger 



Fia. 322. ARTICULAR SURFACES OF TIBIA AND FIBULA WHICH 



ARE OPPOSED TO THE TALUS. 



