346 



THE ARTICULATIONS, OR JOINTS 



Extension of the tarsal bones upon the tibia and fibula is produced by the Gastrocnemius, 

 Soleus, Plantaris, Tibialis posticus, Peroneus longus and brevis, Flexor longus digitorum, and 

 Flexor longus hallucis; flexion, by the Tibialis anticus, Peroneus tertius, Extensor longus 

 digitorum, and Extensor proprius hallucis 1 (Fig. 269); inversion, in the extended position, is 

 produced by the Tibialis anticus and posticus; and eversion by the Peronei. 



Surface Form. The line of the ankle-joint may be indicated by a transverse line drawn 

 across the front of the lower part of the leg, about half an inch above the level of the tip of the 

 internal malleolus. 



Applied Anatomy. Displacement of the trochlear surface of the astragalus from the tibio- 

 fibular mortise is not of common occurrence, as the ankle-joint is a very strong and powerful 

 articulation, and great force is required to produce dislocation. Nevertheless, dislocation does 

 occasionally occur, both in antero-posterior and a lateral direction. In the latter, which is the 

 most common, fracture is a necessary accompaniment of the injury. The dislocation in these 

 cases is somewhat peculiar, and is not a displacement in a horizontally lateral direction, such as 

 usually occurs in lateral dislocations of ginglymoid joints, but the astragalus undergoes a partial 

 rotation around an antero-posterior axis drawn through its own centre, so that the superior 

 surface, instead of being directed upward, is inclined more or less inward or outward according 

 to the variety of the displacement. 



FIG. 278. Section of the right foot near its inner border, dividing the tibia, astragalus, calcaneus, scaphoid 

 internal cuneiform, and first metatarsal bone, and the first phalanx of the great toe. (After Braune.) 



The ankle-joint is more frequently sprained than any joint in the body, and this may lead 

 to acute synovitis. In these cases, when the synovial sac is distended with fluid, the bulging 

 appears principally in the front of the joint, beneath the anterior tendons, and on either side, 

 between the Tibialis anticus and the internal lateral ligament on the inner side, and between the 

 Peroneus tertius and the external lateral ligament on the outer side. In addition to this, bulging 

 frequently occurs posteriorly, and a fluctuating swelling may be detected on either side of the 

 tendo Achillis. 



Chronic synovitis may result from frequent sprains, and when once this joint has been sprained 

 it is more liable to a recurrence of the injury than it was before; chronic synovitis may be tuber- 

 culous in its origin, the disease usually commencing in the astragalus and extending to the joint, 

 though it may commence as a synovitis, the result probably of some slight strain in a tuber- 

 culous subject. 



Excision of the ankle-joint is not often performed for two reasons. In the first place, disease 

 of the articulation, for which this operation is indicated, is frequently associated with disease of 

 the tarsal bones, which prevents its performance; and, secondly, the foot after excision is fre- 

 quently of very little use; far less, in fact, than after a Syme's amputation, which is often, there- 

 fore, a preferable operation in these cases. 



1 The student must bear in mind that the Extensor longus dijritorum and Extensor proprius hallucis are 

 extensors of the toes, but flexors of the ankle, and thait the Flexor longus digitorum and Flexor longus hallucia 

 are flexors of the toes, but extensors of the ankle. 



