PRACTICAL CONSIDERATIONS : THE ANKLE-JOINT. 451 



the lateral ligaments (which limit that movement), and further injury may be done to 

 the synovial sac or to the periosteum or to the bones themselves by the forcible 

 impact of the anterior articular edge of the tibia upon the astragalus. Sprain from 

 hyperextension (plantar flexion) is still rarer. 



In sprains from abduction there may be in the severe forms a momentary slight 

 outward subluxation of the astragalus, as the shaft of the fibula is elastic enough to 

 permit of this without fracture. 



The looseness of the synovial sac (which is said to contain normally a relatively 

 larger amount of synovia than any joint in the body), the dependent position of the 

 region, and the remoteness from the centre of circulation make the swelling and 

 therefore the tension of the joint and the pain following sprain very noticeable. 



Disease of the joint is frequent for the same reasons that sprains are frequent and 

 severe. 



In simple (traumatic) synovitis the swelling is marked. It appears first in front 

 beneath the thin anterior ligament, especially towards the outer side just in advance 

 of the lateral ligament, because there the membrane is less bound down by extensor 

 tendons. Later the swelling extends downward towards the dorsum of the foot for 

 an inch or more, the extensor tendons are pushed forward, and a fulness appears on 

 either side of the tendo Achillis which, still later, extends below the malleoli. The 

 posterior swelling is perhaps the most valuable for diagnosis, as it is not so likely as 

 the anterior swelling to be confused with that produced by disease of tendon-sheaths 

 or of separate bones or joints of the tarsus. 



It may be remembered in this connection that the general shape of the swelling 

 in ankle-joint disease is, rudely, like that of an "anklet," — horizontal, — while the 

 swelling of teno-synovitis is more or less vertical in direction. 



No early distortion of the foot is produced, as the capacity of the joint is but 

 little influenced by position ; but later the calf muscles are apt to overcome the 

 anterior tibial group and to draw up the heel, causing " pointing" of the toes. 



Tuberculosis is common, and is unfavorable in its course because of the ana- 

 tomical conditions above recited, the proximity of the numerous tendon-sheaths, the 

 complex synovial sacs of the tarsus, and the large amount of cancellous tissue in the 

 neighboring bones, and also because of the difficulty of securing complete rest and at 

 the same time keeping up the general health. 



Excision is rarely performed, and is unsatisfactory ; but arthredomy , done 

 through longitudinal incisions in front of both malleoli, and with division of the 

 malleoli themselves, or removal of the astragalus, if it is diseased, has been followed 

 by good results. If the astragalus is to be removed and the malleoli spared (which 

 is often desirable on account of the proximity of the epiphyseal lines), the lateral 

 ligaments will have to be divided. By one or other of these plans ample access to 

 the interior of the joint can be obtained. Syme's amputation is, however, pre- 

 ferred by many surgeons, if ankle-joint disease is at all extensive. 



The horizontal line of the ankle-joint is about half an inch above the tip of the 

 internal malleolus and therefore an inch above the tip of the external malleolus. 



The Joints of the Tarsus, Metatarsus, and Phalanges. — Dislocations of 

 the astragalus — tibio-tarsal dislocations — have been described in connection with the 

 ankle-joint. 



Siibastragaloid dislocations — i. e. , of the calcaneum and scaphoid from the astrag- 

 alus — are almost always either inward and backward or outward and backward, 

 chiefly because of the shape of the opposing articular surfaces of the calcaneum and 

 astragalus. The upper surface of the os calcis, as it advances forward, descends 

 suddenly from a superior to an inferior level, giving the articular processes an oblique 

 — i.e., approximately vertical — direction, to which, of course, the direction of the 

 articular facets on the under surface of the astragalus corresponds. 



It is obvious that much more resistance is offered to anterior displacement of 

 the calcaneum than to displacement in the opposite direction, and, in fact, only two 

 examples of forward subastragaloid dislocation have been recorded. 



The astragalo-scaphoid joint is involved also, but the rounded head of the 

 astragalus offers but little resistance to the backward or lateral movement of the 

 scaphoid, which, moreover, is held firmly in connection with the os calcis, and carried 



