THE ARTICULATIONS OF THE TARSUS 347 



V. The Articulations of the Tarsus (Articulationes Intertarseae) 



(Figs. 276.. 277). 



1. THE ARTICULATION OF THE Os CALCIS AND ASTRAGALUS, OR THE CALCANEO- 



ASTRAGALOID ARTICULATION (ARTICULATIO TALOCALCANEA) (Fig. 276). 



The articulations between the os calcis and astragalus are two in number 

 anterior and posterior. They are arthrodial joints. The bones are connected 

 by a capsule (capsula articular is), -which is at certain points accentuated into 

 definite ligaments. There are five ligaments in this articulation : 



External Calcaneo-astragaloid. Anterior Calcaneo-astragaloid. 



Internal Calcaneo-astragaloid. Posterior Calcaneo-astragaloid. 



Interosseous. 



The external calcaneo-astragaloid ligament (ligamentumtalocalcaneum laterale) 

 (Fig. 277) is a short, strong, fasciculus passing from the outer surface of the 

 astragalus, immediately beneath its external malleolar facet, to the outer surface 

 of the os calcis. It is placed in front of the middle fasciculus of the external 

 lateral ligament of the ankle-joint, with the fibres of which it is parallel. 



The internal calcaneo-astragaloid ligament (ligamentum talocalcaneum mediate) 

 is a band of fibres connecting the internal tubercle of the back of the astragalus 

 with the back of the sustentaculum tali. Its fibres blend w r ith those of the inferior 

 calcaneoscaphoid ligament. 



The anterior calcaneo-astragaloid ligament (ligamentum talocalcaneum an- 

 terius) passes from the front and outer surface of the neck of the astragalus to 

 the superior surface of the os calcis. 



The posterior calcaneo-astragaloid ligament (ligamentum talocalcaneum pos- 

 terius) connects the external tubercle of the astragalus with the upper and inner 

 part of the os calcis; it is a short band, the fibres of which radiate from their 

 narrow attachment to the astragalus. 



The interosseous ligament (ligamentum talocalcaneum interosseum) (Fig. 280) 

 forms the chief bond of union between the bones. It consists of numerous 

 vertical and oblique fibres attached by one extremity to the groove between 

 the articulating facets on the under surface of the astragalus; by the other to 

 a corresponding depression on the upper surface of the os calcis. It is very 

 thick and strong, being at least an inch in breadth from side to side, and serves 

 to unite the os calcis and astragalus solidly together. 



Synovial Membrane. The synovial membranes (Fig. 280) are two in number, one for the 

 posterior calcaneo-astragaloid articulation, a second for the anterior calcaneo-astragaloid joint. 

 The latter synovial membrane is continued forward between the contiguous surfaces of the 

 astragalus and scaphoid bones. 



Movements. The movements permitted between the astragalus and os calcis are limited to 

 a gliding of the one bone on the other in a direction from before backward, and from side to side. 



2. THE ARTICULATION OF THE Os CALCIS WITH THE CUBOID (ARTICULATIO 

 CALCANEOCUBOIDEA) (Fig. 276). 



In this joint the articular capsule (capsula articmaris) is strengthened at certain 

 points by definite ligaments. 



The ligaments connecting the os calcis with the cuboid are four in number: 



Superior or Dorsal Calcaneocuboid. T PI t / L n g Calcaneocuboid. 

 The Internal Calcaneocuboid. I Short Calcaneocuboid. 



