474 SURGICAL APPLIED ANATOMY. [Chap. xxm. 



ligament, and by the contact of the astragalus with 

 the tibia. Extension is limited by the anterior fibres 

 of the inner ligament, the anterior and middle parts 

 of the outer ligament, by the anterior part of the 

 capsule, and the contact of the astragalus with the 

 tibia. 



Owing to its exposed position, this joint is very 

 liable to become inflamed from injury or other ex- 

 ternal causes. When inflamed, no distortion is, as a 

 rule, produced, the foot remaining at right angles 

 with the leg. It would appear that this position is 

 due to the circumstance that the flexor and extensor 

 muscles about balance one another, and it does not 

 seem that the capacity of the joint is affected by 

 the posture of the foot. The synovial cavity of the 

 ankle is in communication with the inferior tibio- 

 tibular articulation. 



In connection with the subject of " referred pains," 

 it should be remembered that the nerves supplying 

 the ankle-joint bring that articulation into relation 

 with two great plexuses, with the lumbar plexus 

 through the internal saphenous nerve, and with the 

 sacral plexus through the external division of the 

 anterior tibial nerve. 



Dislocations at the ankle-joint. The foot 

 may be dislocated at the ankle in five directions, 

 which, placed in order of frequency, are, outwards, 

 inwards, backwards, forwards, and upwards between 

 the tibia and fibula. These dislocations are nearly 

 always associated with fracture of either the tibia or 

 fibula, or of both bones. 



1. The lateral dislocations: Outwards, inwards. 

 These luxations differ somewhat from those met with 

 in other joints. In the great majority of cases 

 they consist of a lateral twisting of the foot, of 

 such a kind that the astragalus is rotated beneath the 

 tibio-fibular arch. There is no great removal of the 



