THE ANKLE-JOINT 



297 



laterally to the anterior border and contiguous surface of the lower end of the 

 fibula, some fibres passing along the edge nearly as far as the origin of the anterior 

 talo-fibular ligament. 



The fibres increase in length from above downward. In front it is in relation with the 

 peroneus tertius and deep fascia of the leg, and gives origin to fibres of the anterior ligament of 

 the ankle-joint. Behind, it hes in contact with the interosseous hgament, and comes into con- 

 tact with the articular surface of the talus (see figs. 328 and 329). 



The posterior lateral malleolar ligament (figs. 328 and 334) is very similar 

 to the anterior, extending from the posterior and lateral angle of the lower end 

 of the tibia dowmward and laterally to the lowest 1.5 cm. (^ in.) of the border 

 separating the medial from the posterior surface of the shaft of the fibula, and to 

 the upper part of the posterior border of the lateral malleolus. It is in relation 

 in front with the interosseous ligament; below, it touches the transverse ligament. 



The inferior interosseous ligament is a dense mass of short, felt-like fibres, passing trans- 

 versely between and firmly uniting the opposed rough triangular surfaces at the lower ends of the 



Fig. 329. — Right Ankle-joint, showing the Ligaments. 

 (From dissection by Mr. W. Pearson, of the Royal College of Surgeons' Museum.) 



Superficial fibres of anterior ' 

 lateral malleolar ligament 

 Deep fibres of anterior lateral 

 malieolar ligament 



Anterior talo-fibular ligament 



Posterior talo-fibular ligament 



Calcaneo-fibular ligament 



Deltoid ligament 



tibia and fibula, except for 1 cm. (| in.) at the extremity, where there is a synovial cavity. It 

 extends from the anterior to the posterior lateral malleolar Ugaments, reaching upward 4 cm. 

 (Ij in.) in front, but onlv half this height behind. 



The transverse ligament (fig. 331) is a strong rounded band, attached to nearly the whole 

 length of the inferior border of the posterior surface of the tibia, just above the articular facet 

 for the talus. It then inclines a httle forward and downward, to be attached to the medial 

 surface of the lateral malleolus, just above the fossa, and into the upper part of the fossa itself. 



The synovial membrane is continuous with that of the ankle-joint; it projects upward 

 between the bones beyond their articular facets as high as the inferior interosseous hgament. 



The nerve-supply is the same as that of the ankle-joint; the arterial supply is from the 

 peroneal and the anterior peroneal, and sometimes from the anterior tibial, or its lateral malleolar 

 branch. 



Relations.— In front of the inferior tibio-fibular joint are the anterior peroneal artery and 

 the tendon of the peroneus tertius, and behind it are the posterior peroneal artery and the pad 

 of fat which lies in front of the tendo AchilUs. j j j a 



The movement permitted at this joint is a mere ghding, chiefly in an upward and downward 

 direction, of the fibula on the tibia. The bones are firmly braced together and yet form a shghtly 

 yielding arch, thus allowing a shght side to side expansion during extreme flexion, when the 

 broad part of the talus is brought under the arch, by the upward ghding of the fibula on the 

 tibia. To this end the direction of the fibres of the lateral malleolar Ugaments is downward 

 from tibia to fibula. This mechanical arrangement secures perfect contact of the articular 

 surfaces of the ankle-joint in all positions of the foot. 



4. THE ANKLE-JOINT 



QXdiSS.—Diarthrosis. SnhdWxsion.—Ginglymxis. 



The ankle [articulatio talo-cruralis] is a perfect ginglj^mus or hinge joint. 

 The bones which enter into its formation are: the lower extremity and medial 

 malleolus of the tibia, and the lateral malleolus of the fibula, above; and the upper 



