152 JOINT OF THE ANKLE. 



is tipped with cartilage, and convex in the ver- strong, nay, in some respects stronger, than if it 

 tical direction, being received upon a corres- had been formed out of solid bone, 

 ponding concavity on the outer side of the The ligaments which connect the tenon and 

 astragalus; upon the lower and back part of mortise together, or to speak more literally, 

 this inner surface may be seen a deep depres- which tie the tibia and fibula with the tarsus, 

 sion, where the posterior fibulo-tarsal ligament are five in number, namely, two tibio-tarsal 

 arises ; the anterior edge of the malleolus is and three fibulo-tarsal ligaments, 

 sharp, and gives origin to the anterior fibulo- 1. The internal tibio-tarsal ligament is also 

 tarsal ligament ; the posterior edge is marked called the internal lateral, and by Weitbrecht 

 by a deep groove, which transmits the tendons the deltoid ligament. There is, however, no 

 of the peronei muscles, longus and brevis. reason why we should not apply to it likewise 

 The apex of the malleolus is below, and gives that principle of nomenclature which is so gene- 

 origin to the middle fibulo-tarsal ligament. rally and with such advantage applied to other 

 The astragalus enters into the formation of ligaments. It arises by a truncated apex from 

 the ankle-joint by its superior surface, and a the point of the inner malleolus, and from the 

 portion of its two lateral surfaces. On the little fossa at its outer surface ; its fibres change 

 superior surface we observe, anteriorly, a well as they proceed downwards and are fixed into 

 marked groove forming part of the neck of the the inner surface of the astragalus and os calcis, 

 astragalus ; into this groove the anterior tibio- some proceeding as far forwards even as the 

 tarsal ligament is inserted. Immediately be- scaphoid bone. The posterior fibres are strong 

 hind the groove we meet with an articulating but short ; the anterior are much larger and 

 eminence of an oblong quadrilateral form, an not so thick. Its internal surface is lined by 

 inch and a half in itsantero-posterior, and about the synovial membrane of the joint; and on its 

 an inch and a quarter in its transverse measure- internal surface it is covered by the tendon of 

 ment; (this transverse measurement is, however, the tibialis posticus, and it sends some of its 

 a little greater in front than behind ;) the emi- fibres to the > sheath of the flexor longus 

 nence is remarkably convex from before back- digitorum tendon. In flexion of the leg the 

 wards, and concave from side to side; the outer anterior fibres are relaxed, and the posterior are 

 edge somewhat more elevated than the inner ; rendered tense : in extension the reverse of 

 it is completely covered with cartilage, and cor- course takes place. 2. The anterior tibio- 

 responds to the articulating cavity upon the in- tarsal ligament (l>g. tibio-tarsal, Cloquet) con- 

 ferior exremity of the tibia. Upon the inner sists of a few loose fibres scattered over the 

 side of the astragalus, we find a small articu- synovial membrane, and in some instances so 

 lating surface of a triangular form, with the delicate and so separated by pellicles of fat as 

 base above and apex below ; it is convex in to be scarcely perceptible. They arise from 

 the vertical direction, and is tipped with car- the fore part of the inner malleolus and the 

 tilage prolonged ftom the superior surface : adjacent anterior portion of the tibia, and de- 

 upon thetriangular surface the internal malleolus scend obliquely downwards and outwards to 

 plays; the remaining portion of the inner side be inserted into the neck of the astragalus. 

 of the astragalus is rough, and occupied chiefly This ligament is covered anteriorly by the ten- 

 by the insertion of the internal tibio-tarsal dons of the tibialis anticus, extensor proprius 

 ligament. The external side of the astragalus pollicis, and extensor digitorum longus : poste- 

 is also marked by an articulating surface of a riorly it is in contact with the synovial mem- 

 much greater size for the reception of the ex- brane. 3. The anterior fibulo-tarsal ligament 

 ternal malleolus : it too is of a triangular form (lig. fibula anterius, Weitb., anterior external 

 with the base above ; concave in the vertical, lateral, Boyer) arises from the anterior edge of 

 and slightly convex in the antero-posterior the outer malleolus, a few lines from its ex- 

 direction, tremity; it descends obliquely forwards and 

 b. Ligaments. We have already compared inwards, and is fixed into the astragalus imme- 

 the mechanism of this joint to that of the tenon diately in front of the articulating surface which 

 and mortise ; the mortise cavity, however, is not, receives the fibula : it is scarcely an inch in 

 as we have seen, cut out of a solid bone, but length, of an oblong quadrilateral form, and is 

 being formed in great part in the lower extremity frequently subdivided into two distinct parts, 

 of the tibia, is completed on the outer side by In extension of the foot it is rendered tense ; 

 the fibula, which is firmly united with the tibia in flexion it is relaxed. 4. The middle fibulo- 

 by strong ligaments, forming what is called the tarsal ligament (lig. fibula medium perpen- 

 inferiortibto-fibular articulation. We shall not diculare, Weitb., external lateral ligament, 

 now describe the ligaments which here unite the Cloq.) is a round fasciculus of fibres having 

 tibia and fibula, referring to the article on the almost the appearance of a tendon which arises 

 TIBIO-FIBULAR ARTICULATION ; but we must from the apex of the external malleolus, de- 

 observe that, however it may be advisable, in scends obliquely backwards, and is attached 

 anatomical descriptions, to separate this last to the outside of the os calcis. It does 

 named articulation from the ankle-joint, they not appear to us that in any position of the 

 are perfectly inseparable in their functions, the joint this ligament takes a perpendicular course, 

 integrity of the latter being essentially dependent although that epithet has been applied to it by 

 on that of the former : indeed it may be said, Weitbrecht. It is related superficially to the 

 that, by virtue of the great strength of the liga- peroneus longus tendon, and by its deep sur- 

 mentotis connexion between the tibia and fibula face to the synovial membrane, to the astra- 

 in the former articulation, the mortise is as gains, and os calcis. In flexion of the foot this 



