DISSECTING MANUAL. 



may extend upward to the superior joint; above its upper 

 margin is an oval aperture, about an inch long, for vessels and 

 nerves; in its lower part is a small opening for vessels. Infe- 

 riorly, it runs into the interosseous ligament. [304] 



The inferior joint is between the lower ends of the tibia and 

 fibula and does not always have articular cartilage ; when pres- 

 ent the cartilage is only a narrow strip at the lower end of each 

 bone, continuous with that of the ankle joint. Most of the 

 opposing surfaces are rough and non-articular. The support- 

 ing ligaments are the following: anterior inferior tibio-fibular, 

 fibres running downward and outward from the front of the 

 lower end of the tibia to the front of the external malleolus; 

 posterior inferior tibio-fibular, similar fibres posteriorly; trans- 

 verse inferior tibio-fibular, running from the posterior inferior 

 border of the tibia to the upper end of the pit on the postero- 

 interior aspect of the external malleolus; interosseous, fibres 

 connecting the rough opposing surfaces and in contact with the 

 others. The synovial membrane lining it is prolonged from the 

 ankle joint. [304] 



Ankle Joint. This is a ginglymus diarthrosis. The lower 

 ends of the tibia and fibula, with the transverse inferior tibio- 

 fibular ligament, form a three-sided socket, which is widest in 

 front at its highest part, for the upper surface and sides of the 

 astragalus. Its synovial membrane lines the capsule, communi- 

 cates with the inferior tibio-fibular joint, and covers the fatty 

 pads at the front and back and also above, in the angle between 

 the three bones. Its capsule is formed by the following liga- 

 ments: The anterior ligament is very thin and extends from 

 the lower border of the tibia to the upper border of the head of 

 the astragalus. The posterior ligament connects the contiguous 

 borders of the tibia and astragalus; many fibres radiate inward 

 from the external malleolus. [306] 



The external lateral ligament is strong and divisible into three 

 fasciculi. The anterior, the shortest, runs from the anterior 

 border of the malleolus to the astragalus just in front of its 



[264] 



