ARTICULATIONS 333 



(Fig. 126). Its proximal surface, therefore, is smooth and 

 covered with synovial membrane; its distal surface is sup- 

 ported by the tendon of the tibialis posterior. This ligament 

 has an important part to play in maintaining the integrity 

 of the longitudinal arch of the foot. Posteriorly it is attached 

 to the fore border of the sustentaculum tali, whilst anteriorly 

 it is fixed to the distal surface of the navicular bone. 



The lateral calcaneo- navicular ligament (O.T. external 

 calcaneo- scaphoid ligament} also forms a small part of the 

 socket for the head of the talus. It is placed deeply in 

 the anterior part of the depression between the calcaneus 

 and the head of the talus, and is the medial part of a 

 V-shaped band, the ligamentum bifurcatum, which springs 

 from the anterior part of the proximal surface of the cal- 

 caneus and immediately divides into a medial or navicular 

 part and a lateral or cuboid portion. The medial part, here 

 called the lateral calcaneo-navicular ligament, is continuous 

 below and medially with the plantar calcaneo-navicular 

 ligament, and dorsally with the talo-navicular ligament. 



Calcaneo-cuboid Articulation. In this joint the concavo- 

 convex surface on the fore aspect of the calcaneus articulates 

 with the corresponding surface on the posterior aspect of the 

 os cuboideum. It is a distinct joint, that is, its cavity 

 does not communicate with the cavities of neighbouring 

 joints. The ligaments which bind the two bones together 

 are : 



1. Capsula articularis. 



2. Ligamentum calcaneo-cuboideum plantare. 



3. Ligamentum plantare longum. 



The capsule completely surrounds the joint and its dorsal 

 and medial parts, which are somewhat thickened and are 

 sometimes called the dorsal and medial ligaments of the 

 joint. The medial ligament is the lateral part of the lig. 

 bifurcatum mentioned above. 



The long plantar ligament springs from the distal surface 

 of the calcaneus, anterior to the medial and lateral processes 

 of the tuber calcanei. It extends forwards to the distal 

 surface of the cuboid bone where it broadens out and is 

 for the most part attached to the tuberosity of that bone. 

 Numerous strong fibres, however, are prolonged anteriorly, 

 across the tendon of the peronseus longus, to gain attach- 

 ment to the bases of the three intermediate metatarsal bones. 



