Chap, xxiii.] THE ANKLE AND FOOT. 489 



three cases have been described of dislocation of the 

 internal bone upwards and backwards, together with 

 a like displacement of all the metatarsals. 



One or more of the metatarsal bones may be 

 luxated, or the entire series may be displaced upwards, 

 downwards, inwards, or outwards, the first-named 

 lesion being the most common. In rarer instances, 

 one bone has been thrown in one direction and its 

 fellow or fellows in another. 



Dislocation of the first phalanx of the great toe 

 is often very difficult to reduce, as is also the case in 

 the corresponding luxation in the thumb. When the 

 displacement is dorsal, the difficulty is probably due 

 to the sesamoid bones, which in this joint take the 

 place of the glenoid ligament or fibro-cartilaginous 

 plate of the other toes. " Like the glenoid ligaments, 

 the sesamoid bones are much more firmly connected 

 with the phalanx than with the metatarsal bone, and 

 thus get torn away and shut back behind the head of 

 the metatarsal bone ; or it may be that the sesamoid 

 bones, retaining their connections with the lateral 

 ligaments of the joint as well as with the short flexor 

 tendons, are separated from one another, and so allow 

 the head of the metatarsal bone to pass forwards, and 

 thus become nipped, as it were, in a button-hole 

 between them " (Henry Morris). 



There are six synovial cavities in the foot, 

 excluding that of the ankle-joint, viz., one for the 

 posterior calcaneo-astragaloid joint, a second for the 

 anterior calcaneo-astragaloid and astragalo-scaphoid 

 joints, a third between the os calcis and cuboid, a 

 fourth between the latter bone and the two outer 

 metatarsals, a fifth for the joint between the inner 

 cuneiform and first metatarsal bones, and a sixth for 

 the remaining articulations (Fig. 56). These synovial 

 cavities tend greatly to diffuse disease among the 

 various bones of the foot when once one bone has 



