THE LOWER LIMB 



5S1 



facet on the internal aspect of the inferior surface of the head 

 of the astragalus. This surface of the ligament is covered by 

 synovial membrane, and forms part of the articular socket for 

 the head of the astragalus. It has a smooth, polished appearance, 

 and presents no indication of its fibrous structure. The inferior 

 or superficial surface, on the other hand, has the ordinary fibrous 

 appearance of a ligament, and is in close contact with the tendon 

 of the tibialis posticus, which is a powerful auxiliary to the ligament 

 in supporting the antero-posterior arch of the foot. The spring 

 ligament sometimes contains a sesamoid fibro-cartilage, which 

 occasionally becbmes ossified. 



External Calcaneo-navicular 

 Ligament 



Facet for Spring Ligament 



Fig. 269.- 



Tendon of Tibialis Posticus 



Inferior Calcaneo-navicular or * 

 Spring Ligament 



■.Interosseous Lig^ament 



■The Inferior Calcaneo-n.wicular or Spring Ligament 

 OF THE Left Foot (Superior View), 



The astragalo-navicular, external or superior calcaneo-navicular, 

 and internal or inferior calcaneo-navicular ligaments form together 

 a capsule for the astragalo-navicular joint. 



The synovial membrane is continuous with the sjnovial mem- 

 brane of the anterior astragalo-calcaneal joint. 



Arterial Supply. — ^The anterior tibial, external tarsal branch of 

 the dorsalis pedis, and internal plantar arteries. 



Nerve-supply. — ^The internal plantar and the external division 

 of the dorsalis pedis ner\'e. 



The movements at this joint will be described with those at the 

 calcaneo-cuboid joint. 



