THE SOLE OF THE FOOT. 279 



orly a surface convex from before backwards for the cor- 

 responding articular surface of the tibia ; laterally are 

 two articular surfaces corresponding with those of the 

 malleoli, the external one being the larger. The liga- 

 ments are an external lateral, consisting of three fas- 

 ciculi ; an internal, or deltoid, radiating from the inner 

 malleolus, to be attached to the scaphoid, os calcis, and 

 astragalus ; anteriorly are a few fibres closing in the ar- 

 ticulation ; posteriorly the joint is shut in by the trans- 

 verse ligament of the inferior tibio-fibular articulation. 

 The synovial membrane invests the inner surface of the 

 ligaments and articular cartilages, and owing to the 

 great laxity of the anterior and posterior ligaments it 

 readily bulges through them, consequently the joint is 

 easily reached from either aspect, and in cases of syno- 

 vitis the membrane usually protrudes in front between 

 the malleoli and again behind the external malleolus. 



Dislocation at the Tibio-tarsal Articulation that is to 

 say, dislocation of the entire foot from the bones of the 

 leg is almost invariably associated with fracture of one 

 or other malleoli, which can be readily understood from 

 the shape and extent of motion allowed at the joint. It 

 is a result of the foot being twisted in running or walk- 

 ing, and may either be outwards, when the lower end of 

 the fibula is broken, the inner malleolus or internal lat- 

 eral ligament torn ; internal, when there is no fracture 

 of the fibula, but the lower end of the tibia is broken ; 

 backwards, when both malleoli are broken, and the heel 

 projecting; and forwards, when the astragalus is thrown 

 in front of the tibia. 



Excision of the Ankle-joint (tibio-tarsal). The seat of 

 the disease can be reached by a variety of incisions ; but 

 the object to be attained is to save the tendons, in order 



