S 6 4 



APPLIED ANATOMY. 



height and alights on the sole of the foot the astragalus or os calcis of the posterior 

 pillar is fractured while the bones of the anterior pillar escape. The internal part 

 of the foot is more liable to give way than the external part because the external part is 

 practically in contact with the ground while the internal part has as its support ligaments 

 and muscles, and when these latter give way it is the inner side of the foot which sinks. 

 This is still more favored by the position of the tuberosities of the os calcis with refer- 

 ence to the ankle-joint; they are not directly beneath it, but somewhat to its outer side. 



THE JOINTS AND LIGAMENTS OF THE FOOT. 



The amount of movement that takes place between the bones of the foot is not 

 as great as would be expected from their number. It is only in the subastragaloid 

 joint that any considerable motion takes place, while a less amount occurs at the 



Tendo calcaneus (Achillis) 



Peroneus longus and brevis 



Posterior articular surface 

 on os calcis 



Anterior articular surface 

 on os calcis 



Plantar vessels and nerves 



Flexor longus hallucis 

 Flexor longus digitorum 



Interosseous astragalo- 

 calcaneal ligament 



Inferior calcaneo-scaphoid 

 ligament 



Posterior tibial tendon 

 Scaphoid 



Anterior tibial tendon 



Extensor longus hallucis 

 Anterior tibial vessels 



FIG. 582. The subastragaloid joint; lower surface. The astragalus has been removed. 



midtarsal joint. The contiguous tarsal bones are joined by numerous band-like, 

 capsular, and interosseous ligaments which allow a limited amount of movement 

 between them. In the aggregate these movements are considerable and make the 

 foot as a whole quite flexible. 



The Subastragaloid Joint (Articulatio talo-calcaneo-navicularis). This 

 is a horizontal joint formed by the astragalus above and the os calcis and navicular 

 (scaphoid) below and in front. It runs obliquely forward and inward. The astrag- 

 alus is not wedged in between the os calcis and scaphoid like the keystone of an 

 arch, but the foot moves freely beneath it. It has an inward motion of adduction 

 around an anteroposterior or longitudinal axis with internal rotation around a vertical 

 axis, and an outward motion of abduction with external rotation. The abduction 

 and adduction movements cannot occur independently of rotation, they are com- 

 bined. The astragalus is joined to the os calcis below and scaphoid below and in 



