642 



DISSECTION OF THE LEG. 



the tibia and fibula, and consists of transverse yellowish fibres distinct 

 from the posterior ligament. It is fixed on one side to the end of the 

 fibula above the pit : and on the other it is inserted into the contiguous 

 part of the tibia, and into the posterior edge of the articular surface so as 

 to assist in deepening the hollow into which the astragalus is received. 



The interosseous ligament fills the interval between the bones of the 

 leg, and serves as an aponeurotic partition between the muscles on the 

 front and back of the leg. Its fibres are directed downwards for the most 

 part from the tibia to the inner surface of the fibula : but some few cross 

 in the opposite direction. 



Internally it is fixed to the outer edge of the tibia : and externally, to 

 the oblique line on the inner surface of the fibula along the upper three- 

 fourths, but to the posterior border along the lower fourth of that bone. 



Both superiorly and inferiorly is an aperture which transmits vessels. 

 The upper opening, about an inch in length, lies along the neck of the 

 fibula, and gives passage to the anterior tibial vessels. The lower aper- 

 ture is close to the fibula, about an inch above the lower end, and is only 

 large enough for the small anterior peroneal vessels. 



Some strong irregular bundles of fibres, the inferior interosseous liga- 

 ment, extend between the bones below the aperture for the anterior pero- 

 neal artery. It may be seen after the examination of the ankle joint by 

 sawing longitudinally the lower ends of the leg bones. 



Movement. Very little movement is allowed in the tibio-peroneal articu- 

 lations, as the chief use of the fibula is to give security to the ankle joint 

 and attachment to muscles of the leg. 



In the upper joint there is a slight gliding from before back. In the 

 lower articulation the ligaments permit some yielding of the fibula to the 

 pressure of the astragalus, as when the weight of the body is thrown on 

 the inner side of the foot ; but if the force is violent the lower fourth of 



that bone will be fractured sooner 

 than the ligaments. 



ARTICULATION OF THE ANKLE 

 (fig. 221). Like the knee, the 

 ankle is a ginglymoid or hinge joint. 

 In this joint the upper surface of the 

 astragalus is received into an arch 

 formed by the lower ends of the 

 tibia and fibula ; and the four liga- 

 ments belonging to this kind of 

 articulation connect together the 

 bones. 



Dissection. To make the dissec- 

 tion required for the ligaments of 

 the ankle joint, the muscles, and the 

 fibrous tissue and vessels must be 

 removed from the front and back of 

 the articulation. 



For the purpose of defining the 

 lateral ligaments, the limb must be 

 placed first on one side and then on 

 the other. The internal ligament 

 is wide and strong, and lies beneath 

 the tendon of the tibialis posticus. 



Fig. 221. 



INTERNAL LATERAL LIGAMENT OP THE ANKLE 

 (altered from Hourgery). 



1. Posterior piece. 



2. Middle piece. 



3. Anterior piece of the inner ligament. 



4. Inferior calcaneo-scaphoid ligament. 



