TIBIO-FIBULAIl ARTICULATIONS. 



1119 



membrane of the knee joint is brought into 

 this close relationship with that of the tibio- 

 fibular articulation, by means of a prolonga- 

 tion which passes downwards from the former 

 around the tendon of the poplitceus muscle ; 

 and when a communication does exist between 

 the two articulations, it will therefore be found 

 at the posterior aspect of the head of the 

 fibula. 



This anatomical arrangement has an import- 

 ant bearing on a disputed point of practice, 

 viz. the extirpation of the head of the fibula 

 in amputations of the leg near the knee joint. 

 This proceeding, recommended originally by 

 Larrey and Garriques, and subsequently re- 

 vived by Mr. Guthrie, has been opposed by 

 Mr. Adams of Dublin, who, appealing to the 

 anatomical peculiarities just described, makes 

 them the grounds for rejecting altogether the 

 innovation in question. (Vide "ABNORMAL 

 CONDITION OF THE KNEE JOINT," vol. iii. 

 p. 50.) 



INFERIOR TIBIO-FIBULAR ARTICULATION. 

 This articulation is intimately connected 

 with that of the ankle, from which, although 

 anatomically distinct, it cannot virtually be 

 separated. 



The tibia and the fibula, at the lower part of 

 the leg, are closely connected for a consider- 

 able portion of their extent. The tibia pre- 

 sents, on its external aspect and inferiorly, a 

 triangular-shaped surface, two inches in verti- 

 cal height, and concave from side to side : 

 superiorly, or towards the apex of this space, 

 it presents a rough and scabrous surface ; but 

 inferiorly it is smooth and encrusted, in the 

 recent state, with articular cartilage. The 

 inner surface of the lower end of the fibula is 

 of similar shape, but convex ; it is rough su- 

 periorly, and smooth inferiorly. Here the two 

 bones form an arthrodial articulation. 



a. The cartilage, which in this situation in- 

 vests the opposed surfaces of the tibia and 

 fibula, is continuous with that which covers 

 the inferior surface of the tibia. It is also lined 

 by b. synovia! membrane prolonged upwards 

 from the ankle joint, and which forms a small 

 cul-de-sac in the tibio-fibular articulation. 

 The rough irregular surfaces, on the bones 

 above the line of reflexion of the synovial 

 membrane, have the fibres of a strong inter- 

 osseous ligament implanted into them. 



c. The ligaments of the inferior tibio-fibular 

 articulation are three in number ; 1. an ante- 

 rior, 2. a posterior, and 3. an interosseous. 



1, Anterior tibio-fibular ligament. The fibres 

 of this ligament pursue a direction downwards 

 and outwards, from the anterior margin of the 

 small articulating surface on the tibia to the 

 outer malleolus ; and as the lower margin of 

 this ligament projects below the level of the 

 tibia, it deepens somewhat the cavity for the 

 reception of the astragalus. The tendon of 

 the perona3us tertius muscle covers this liga- 

 ment in front. 



2. Posterior tibio-fibular ligament. This is a 

 strong, round, fibro-cartilaginous cord, which 

 passes from one malleolus to the other in an 

 arched manner, having a concavity directed 



downwards, and connected with the posterior 

 ligament of the ankle joint, and a convexity 

 which adheres uniformly to the posterior arti- 

 cular margins of the tibia and fibula. This 

 ligament not only connects the two bones to 

 each other, but it also, like circumferential 

 fibro-cartilages elsewhere, serves the purpose 

 of deepening the mortice-shaped cavity of the 

 ankle joint which it borders. It likewise pre- 

 vents the immediate contact of the osseous 

 surfaces in forced extension of the foot, being 

 interposed between the bones as an elastic 

 cushion. 



3. Interosseous tibio-fibular ligament, This 

 is composed of short transverse bands firmly 

 implanted, at right angles, into the opposed 

 rough surfaces on the bones already described. 

 Superiorly, the fibres of this ligament extend 

 nearly as far as the lower margin of the inter- 

 osseous membrane, (separated from it by a 

 small interval, through which passes a branch 

 of the fibular artery), whilst inferiorly they 

 are limited by the direct contact of the two 

 bones of the leg, which they serve to bind 

 firmly together. In order to exhibit this 

 structure, either of two methods may be 

 adopted ; the bones of the leg may be sawn 

 across about their centres, and then forcibly 

 torn asunder, (in this way the ligament may be 

 seen, and its powers of resistance appreciated), 

 or the ligament may be exhibited in situ, by 

 making a vertical, transverse, section of both 

 bones, traversing the two malleoli, and also 

 the joint of the ankle.* 



Mechanism of the tibio-fibular articulations. 

 The movements of the fibula on the tibia are 

 extremely limited ; this is in accordance with 

 the general plan on which the skeleton of the 

 lower extremity is formed, its use being to 

 serve as an organ of support, and of locomo- 

 tion, only. The bones of the leg are connected 

 together by the intervention of ligaments, (not 

 consolidated together as in the arrangement 

 met with in a few of the Mammalia), and thus 

 a greater degree of elasticity is obtained without 

 any sacrifice of strength ; and it may be pre- 

 sumed that the slight degree of yielding and of 

 gliding motion, which is permitted in the tibio- 

 fibular articulations, may occasionally serve to 

 diffuse, and to lessen the intensity of shocks 

 applied to the lower extremity, and may thus 

 diminish its liability to injury, especially to 

 fracture. 



Dislocation of the fibula, at the upper 

 tibio-fibular articulation, has occasionally, but 

 rarely, been met with as the result of injury. 

 Sir A. Cooper mentions a case of compound 

 fracture of the tibia, where this complication 

 was observed ; but the rarity of dislocations 

 in this situation, is accounted for by the cir- 

 cumstance, that the fibula, owing to its com- 

 parative slightness, almost invariably breaks, 

 on the application of a force far short of what 

 suffices to rupture its ligamentous connections 

 with the tibia. 



The mechanism of the inferior tibio-filndar 

 articulation is inseparably connected with 



* See fig. 61. p. 163. vol. i. 



