JOINT OF THE ANKLE. 



151 



of the veins, and the possibility of mistaking 

 one for the other, should be remembered by 

 the surgeon. In front of the inner malleolus 

 we observe one or two openings in the fascia, 

 through which small branches of communication 

 pass between the superficial and deep veins; 

 these, no doubt, are the principal channels 

 through which the venous blood of the integu- 

 ments about the foot and instep is returned, 

 after the operation of tying the great saphena 

 vein. 



e. Lymphatics. The lymphatics consist like- 

 wise of two sets ; the one lying beneath the 

 integuments and scattered irregularly over the 

 region ; the other lying beneath the fascia, and 

 for the most part accompanying the blood- 

 vessels. Some anatomists speak of a lymphatic 

 gland lying upon the instep, and receiving 

 several of these deep absorbents ; in the majo- 

 rity of cases there is no such gland, and its 

 existence in any appears to us extremely 

 doubtful. 



f. Nerves. The nerves in this region have 

 the same general distribution as the arteries. 

 In our account of the larger arteries, we have 

 already minutely assigned the relation which 

 their accompanying nerves bear to them. We 

 may thus briefly enumerate them : in front, 

 the musculo-cutaneous and anterior tibial ; on 

 the inner side the terminal ramifications of the 

 internal saphenus and the posterior tibial ; and 

 on the outside, the terminal branches of the 

 external saphenus. For further particulars re- 

 specting the nerves, we refer to the articles 

 LUMBAR NERVES; SACRAL NERVES. 



For the BIBLIOGRAPHY of this article and all 

 others on surgical anatomy, see the Bibliography 

 of ANATOMY (INTRODUCTION.) 



(John E. Brenan.} 



ANKLE, JOINT OF THE. (Normal ana- 

 tomy.) (Fr. articulation du coude-pied. Germ. 

 Fussgelenk. Ital. caviglia.} The ankle-joint, or 

 tibio-tarsal articulation, results from the junc- 

 tion of the leg and foot. For reasons which 

 will appear when we come to explain its mo- 

 tions, it is ranked in the excellent and com- 

 prehensive classifications of Bichat and Cloquet 

 as a perfect angular ginglymus. The security 

 of the ankle-joint, more perhaps than of any 

 other in the body, is owing to the peculiar 

 form of its bones, and to their exact adap- 

 tation to each other; in this respect it has 

 aptly been compared to the tenon and mortise 

 joint, so frequently used by mechanics, the 

 strength of which, as is well known, is chiefly 

 owing to the peculiar form and close fitting of 

 its component parts. Upon the '.ipper part of 

 the foot, we meet with, it is said, a true and well 

 defined tenon, and upon the lower part of the 

 leg a tolerably perfect mortise for the reception 

 of the tenon. The comparison, though perhaps 

 not strictly correct, will however assist us in 

 understanding how much the security of this 

 joint depends upon the form and fitting of its 

 bones ; and will explain to the beginner why, 

 in treating of the ankle-joint in particular with 

 a view to demonstrate its use and mechanism, 

 a brief account of its bones becomes part of our 



description no less essential than of its liga- 

 ments themselves. In our account, therefore, 

 of this articulation, we shall, in the first place, 

 describe its bones; next its ligaments; and, 

 lastly, shall offer some remarks upon its me- 

 chanism and uses. 



a. The Bones. Three bones contribute to 

 the formation of the ankle-joint; the tibia and 

 fibula form, by the union of their inferior por- 

 tions, a deep depression, into which the head of 

 the astragalus is received. The tibia, as it ap- 

 proaches the joint, looses gradually its prismatic 

 shape, and assumes a well-defined cubical or 

 quadrangular form. On its lower extremity it 

 presents a quadrilateral articulating cavity, 

 covered in the recent state with cartilage ; this 

 cavity is transversed from before backwards by 

 an obtuse ridge which subdivides it into two 

 smaller cavities. Of the four sides or margins 

 of this articulating cavity, the anterior is almost 

 straight transversely, but convex or rounded off 

 in the vertical direction, with the obvious design 

 of permitting a greater flexion to the foot; the 

 anterior tibio-tarsal ligament arises from this 

 margin. The posterior margin is also straight 

 transversely, but vertically convex, to permit an 

 increased extension to the foot ; the posterior 

 tibio-fibular ligament is connected here : a 

 shallow oblique groove is met with upon the 

 outer part of this surface, for the transmission 

 of the flexor longus pollicis tendon. The ex- 

 ternal side presents a depression for the reception 

 of the fibula ; this articulating portion is pro- 

 longed upwards for nearly an inch, is of a 

 triangular form with the base below ; the sides 

 of the triangle give attachment to the anterior 

 and posterior tibio-fibular ligaments ; and the 

 area of the triangle is rendered rough, except at 

 its lowest part, by the attachment of the inferior 

 interosseous ligament, another strong bond of 

 union between these bones. The inner edge is 

 prolonged downwards nearly an inch in length, 

 forming the prominence known by the name of 

 malleolus internus; this is placed upon a plane 

 superior and anterior to the malleolus externus; 

 it is somewhat flattened in shape, and has one 

 surface looking inwards or towards the mesial 

 line ; this in the living subject is covered only 

 by the integuments ; the outer surface enters 

 into the formation of the joint, hence it is 

 tipped with cartilage to permit the astragalus to 

 play upon it ; the anterior edge is sharp and 

 gives origin to the anterior tibio-tarsal ligament; 

 the posterior edge is traversed by a broad and 

 generally well-marked groove, which transmits 

 the tendons of the tibialis posticus and flexor 

 digitorum longus ; the apex of the malleolus 

 is below, and gives attachment to the deltoid or 

 internal tibio-tarsal ligament. 



Thejibula, as it approaches the foot, becomes 

 suddenly enlarged in size, applies itself firmly 

 to the tibia, and then descends nearly an inch 

 and a half below its point of union with that 

 bone. The prominence formed by the fibula 

 in this situation is named the malleolus externus ; 

 it is much larger than the internal, and placed 

 behind and somewhat below it. The external 

 surface of this fibular malleolus is covered 

 merely by the integuments ; the internal surface 



