ARTICULATION OF THE ASTRAGALUS AND OS CALCIS. 265 



ment passes downwards from the tibia at the internal malleolus, 

 and is inserted into the inside of the astragalus, and also into 

 the os calcis and naviculare. Some of the fibres are blended 

 with those of the sheath for the tendon of the flexor communis ; 

 and some of them have a radiated arrangement, in consequence 

 of which this has been called the deltoid ligament. 



From the fibula three ligaments arise, spoken of collectively 

 as one ligament, external lateral, (ligament-urn triquetrum.) 

 The middle fasciculus, which is strong and thick, passes down- 

 wards from the end of that bone, to be inserted into the outside 

 of the os calcis. The anterior fasciculus passes forwards, and 

 is attached to the astragalus. The posterior fasciculus passes 

 backwards, and is attached to the posterior part of the astragalus. 

 The anterior ligament is a thin membranous layer, in contact 

 with the synovial membrane, it passes from the anterior margin 

 of the tibia and is inserted into the anterior portion of the astra- 

 galus, near the articular surface. No well marked posterior liga- 

 ment exists at this articulation. The transverse ligament sup- 

 plies its place. 



Articulation of the Astragalus and Os Calcis. 



Fig. 69.* The astragalus is attached firmly to 



the* os calcis by very strong and 

 short ligamentous fibres, which arise 

 from the fossa on its under surface, 

 and are inserted into the fossa Be- 

 tween the upper articulating sur- 

 faces of the os calcis. This is called 

 the interosseous. This ligament 

 separates the posterior articulations 

 of the astragalus and os calcis from 

 the anterior. The posterior articulation has a synovial mem- 

 brane exclusively appropriated to it. The anterior articulation 



* An external view of the ankle joint. 1. The tibia. 2. External malleolus 

 of the fibula. 3, 3. Astragalus. 4. Os calcis. 5. Cuboid bone. 6. The ante- 

 rior fasciculus of the external lateral ligament attached to the astragalus. 7. Its 

 middle fasciculus attached to the os calcis. 8. Its posterior fasciculus attached 

 to the astragalus. 9. The anterior ligament of the ankle. 

 23 



