INTEKTAKSAL JOINTS. 



355 



Plantar cal- ( 



caneo-navicular-J 



ligament V. 



Tendon of tibialis 



posterior muscle 



(cut) 



a deeper plane than, the calcaneo-fibular ligament of the ankle-joint. It con- 

 sists of short fibres passing between the adjacent rough lateral margins of the two 

 bones. 



The ligamentum talocalcaneum posterius (Fig. 324) closes the joint-cavity on 

 its posterior aspect. It consists of fibres which radiate from the posterior aspect 

 of the posterior process of the talus to the superior surface of the calcaneus, 

 immediately behind the articular facet. 



The ligamentum talocalcaneum mediale lies obliquely on the medial side of the 

 joint, and consists of fibres which extend from the medial posterior tubercle of the 

 talus to the posterior roughened border of the sustentaculum tali. Some of its 

 fibres become continuous with the plantar calcaneo-navicular ligament. 



The ligamentum talocalcaneum interosseum (Fig. 325) closes the antero-medial 

 aspect of the joint. It is the strongest of the series of ligaments entering into the 

 capsule. Compared with it the other bands are, comparatively speaking, insigni- 

 ficant. Its attachments 

 are to the bottom of each 

 groove, so that it occupies 

 the tarsal canal formed by Navicular bone 

 these opposing grooves. 



A synovial stratum lines 

 the fibrous stratum, and it 

 is distinct from other tarsal 

 synovial membranes. 



Articulatio Talocal- 

 caneonavicularis. This 

 is one of the most import- 

 ant of the joints of the 



foot, not only because the Sustentaculun ^ce for talus 

 talus is here situated in 

 relation to the summit of 

 the an tero- posterior arch 

 of the foot, but because the 

 head of the talus is received 

 into a composite socket 

 made up of the susten- 

 taculum tali, the navicular, 

 and the plantar calcaneo- 

 navicular ligament. 



The articular surface 

 on the head of the talus presents anteriorly a convex rounded facet for articulation 

 with the navicular, inferiorly a convex facet which rests upon the sustentaculum 

 tali, and intermediate between these two there is a triangular facet which 

 articulates with the plantar calcaneo-navicular ligament. All these facets are 

 in continuity with each other, and are in front of the tarsal groove on the inferior 

 surface of the talus. Occasionally a fourth narrow facet is found along the lateral 

 and posterior part of the articular surface of the head of the talus, whereby it 

 articulates with the calcaneo-navicular part of the bifurcate ligament. 



The navicular bone presents a shallow, cup-shaped, articular cavity towards the 

 head of the talus. 



The articular surface of the sustentaculum tali is concave, and is usually marked 

 off into two facets. 



Two ligaments play an important part in binding together the calcaneus and 

 the navicular, although these bones do not directly articulate ; and further, these 

 ligaments provide additional articular surfaces for the head of the talus. These 

 are the two following : 



(a) The ligamentum calcaneonaviculare plantare (Figs. 325 and 326) is an 

 extremely powerful fibro- cartilaginous band. It extends between the anterior 

 margin of the sustentaculum tali and the plantar surface of the navicular. Certain 

 of its upper fibres radiate upwards on the medial surface of the navicular, and 



Articular surface on 

 navicular for head of 

 talus 



\ Calcaneo-navicular part 

 of bifurcate ligament 



Interosseous talo- 



calcaneal 



ligament 



Articular surface 

 on calcaneus for 

 body of talus 



Calcaneus 



FIG. 325. THE COMPOSITE ARTICULAR SOCKET FOR THE HEAD OP 

 THE TALUS. 



