THE REGION OF THE ANKLE AND FOOT 481 



Ossification of the Distal Extremities of the Bones of 

 the Leg. Secondary centres appear in the cartilaginous distal 

 extremities of the tibia and fibula about the second year, and 

 the epiphyses so formed unite with the diaphysis during the 

 nineteenth year. 



As the fibula projects distally beyond the tibia, the epiphyseal 

 lines of the two bones are situated at different levels so that the 

 distal extremity of the fibular diaphysis is in relation to the 

 tibial epiphysis (Fig. 142), and therefore to the joint-cavity 

 when present (p. 482) of the distal tibio-fibular articulation. 

 The fibular diaphysis is sometimes intra-capsular in relation 

 to the ankle-joint. 



The Ankle- Joint. At this joint the talus articulates with 

 the tibia by its superior surface and with the malleoli on each 

 side. The necessary stability is obtained by the downward 

 projection of the malleoli, which descend on each side of the 

 talus and only permit a slight degree of lateral movement. The 

 upper surface of the talus is wider in front than it is behind, and 

 on this account, side to side movements at the ankle-joint occur 

 more freely when the foot is extended than when it is flexed. 



The Capsule of the ankle is relatively weak. Proximally, 

 it is attached to the fibular and tibial epiphyses around the 

 margins of their articular surfaces. Distally, it is attached 

 around the articular surface of the talus except on the anterior 

 aspect of the joint, where it extends on to the neck of the bone 

 (Fig. 144); which is thus in part intra-capsular. 



The synovial membrane lines the interior of the capsule, and 

 anteriorly it is reflected over the intra-capsular part of the neck 

 of the talus. 



The anterior and posterior ligaments of the ankle are special 

 thickenings of the capsule which require no detailed description. 

 The Deltoid Ligament strengthens the medial part of the 

 capsule. It is narrow at its proximal attachment to the medial 

 malleolus, but widens out distally and is attached not only to 

 the talus but also to the sustentaculum tali, the plantar calcaneo- 

 navicular (" spring ") ligament and the navicular bone. 



The Lateral Ligament consists of three separate bands, 

 (i) The anterior talo-fibular ligament stretches from the anterior 

 border of the lateral malleolus to the lateral side of the body 

 of the talus. (2) The calcaneo-Jibular ligament is a cord -like 

 band which extends from the tip of the malleolus to the lateral 

 surface of the calcaneus. (3) The posterior talo-fibular ligament 



