344 



BONES OF THE FOOT. 



over the superior aspect of the joint; the fibres 

 pass with a slight obliquity inwards from the os 

 calcis to the cuboid. 3. The plantar or inferior 

 calcaneo-cuboid ligament, the strongest and 

 largest of the foot ligaments, seems destined 

 not alone for the articulation under considera- 

 tion, but also to strengthen the arch of the 

 tarsus generally on its plantar surface. It is 

 attached behind to the inferior surface of the 

 os calcis, commencing from the angular depres- 

 sion between the two tubercles. After leaving 

 the os calcis a distinction between its superficial 

 and deep fibres becomes very manifest; the 

 former proceed forwards and inwards, pass 

 under the cuboid bone, forming an adhesion to 

 the posterior lip of its groove, then pass under 

 that groove and its contained tendon, and are 

 ultimately inserted into the posterior extremities 

 of the third and fourth metatarsal bones. The 

 deep fibres diverge immediately after they have 

 left the os calcis, and are inserted into the whole 

 inferior surface of the cuboid posterior to the 

 groove. 



It will be observed that the two joints last 

 described lie beside each other in the same 

 line, a circumstance which favours the surgical 

 operation of partial amputation of the foot in 

 that line. Each joint, however, has its proper 

 synovial membrane lining the cartilaginous 

 incrustations of the bones and the articular 

 surfaces of the ligaments; that of the astragalo- 

 scaphoid is the more lax, and indicates the 

 existence of a considerable range of motion in 

 that joint. 



Motions of the tarsal joints. All these 

 joints belong to the class Arthrodia, some of 

 them being planiform. The motion in all is 

 that of simple gliding, limited by the strength, 

 number, and position of the ligaments. The 

 close inspection of the bones of the meta- 

 tarsal row, and the firm ligamentous bands 

 which pass between them, occasion a very 

 limited mobility of the bones of that row. 

 Between the astragalus and os calcis, on the 

 other hand, the motions are much more mani- 

 fest; these are gliding motions in the direction 

 from before backwards and vice versa, or from 

 side to side. \\ hen the foot is turned inwards 

 or outwards the latter motion is called into 

 play, and the gliding in the antero-posterior 

 direction takes place when the weight of the 

 body presses on the foot, causing its elongation 

 and the diminution of the curvature of its 

 antero-posterior arch. When the weight presses, 

 the astragalus glides forward upon the os calcis; 

 when the weight is removed, the bone returns 

 to its firmer condition by gliding backwards. 



But the greatest mobility exists in the articu- 

 lation between the two rows of tarsal bones. 

 There, indeed, the principal motions of the 

 tarsus take place. The motions of the foot, 

 which many have erroneously attributed to a 

 supposed power of lateral motion in the ankle- 

 joint, really take place in this line of articula- 

 tion. When the foot is turned so that its sole 

 is directed outwards, the scaphoid glides from 

 above downwards on the head of the astragalus, 

 the astragalus glides from within outwards on 

 the os calcis, in consequence of which the 



hollow space between the last-named bone and 

 the neck of the astragalus is diminished, the 

 interosseous ligament relaxed, the external 

 lateral ligament of the ankle-joint likewise 

 relaxed, and the internal lateral ligament ren- 

 dered tense. On the other hand, when the 

 sole of the foot is turned inwards, which may 

 be done much more completely than in the 

 opposite direction, the scaphoid glides from 

 below upwards upon the head of the astragalus, 

 the inferior surface of the os calcis is turned 

 inwards, the astragalus glides upon the last- 

 named bone from without inwards, enlarging 

 the interosseous space, stretching the ligament 

 which occupies that space, arid also rendering 

 tense the external lateral ligaments of the ankle- 

 joint. It is therefore natural to expect, as 

 Bichat has remarked, that in those sprains 

 which result from too great inversion or eversion 

 of the foot, the ligaments of the articulations 

 between the tarsal rows should suffer most. 



Tarso-metatarsal articulations. The plane 

 surface on the wedge-shaped tarsal extremity of 

 each metatarsal bone is applied to correspond- 

 ing plane surfaces on the cuneiform bones and 

 the cuboid. The first, second, and third meta- 

 tarsal bones, counting from within outwards, 

 are articulated with the first, second, and third 

 cuneiforms, and the fourth and fifth with the 

 cuboid; the second metatarsal, however, is 

 additionally articulated with the first and third 

 cuneiforms, by its lateral surfaces being, as it 

 were, mortised into a cavity formed by these 

 three bones, and each of the other metatarsal 

 bones is articulated with its fellow on each side 

 of it. These articulations have the following 

 common characters : they are planiform arthro- 

 dise, each articular surface is covered by a thin 

 layer of cartilage, and they all have ligaments 

 similarly arranged in two sets, dorsal and 

 plantar. 



The first tarso-metatarsal articulation has a 

 greater extent of its articular surfaces than those 

 of the others. Its plantar ligament is of great 

 strength and extends from the great cuneiform, 

 directed obliquely forwards and outwards to 

 the first metatarsal bone, continuous posteriorly 

 with the cuneo-scaphoid ligament, and strength- 

 ened by fibres from the tendon of the tibialis 

 posticus, and on the outside by fibres from the 

 tendon of the peroneus longus. The dorsal 

 ligament consists of short and parallel fibres ; its 

 breadth is equal to that of the cuneiform bone ; 

 it is a weak and membranous ligament. This 

 articulation has a synovial membrane distinct 

 from that of the other tarso-metatarsal joints. 



The second tarso-metatarsal articulation is 

 the most solid of all, from the fact of the pos- 

 terior extremity of the metatarsal bone being 

 fitted into the mortise-shaped cavity formed by 

 the cuneiform bones. Its ligaments, it may 

 naturally be expected, are more complicated 

 than those of the other joints of this row ; thus 

 it has three dorsal ligaments, a middle one, 

 possessing common characters with those of the 

 other joints, proceeding directly from behind 

 forwards from the second cuneiform to the 

 second metatarsal bone; the others are ex- 

 tended, one from the internal cuneiform 



