432 THE INFERIOR EXTREMITY 



Calcaneo- cuboid Articulation. In the calcaneo- cuboid 

 joint the concavo-convex surface on the anterior 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, are some- 

 times called the dorsal and medial ligaments of the joint. 

 The medial ligament is the calcaneo cuboid part of the lig. 

 bifurcatum mentioned above. 



The long plantar ligament springs from the plantar surface 

 of the calcaneus, immediately anterior to the tuber calcanei. 

 It extends forwards to the plantar 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 forwards, across the tendon of 

 the peronaeus longus, to gain attachment to the bases of 

 the second, third, and fourth metatarsal bones. The long 

 plantar ligament, therefore, extends over the greater part of the 

 plantar aspect of the lateral portion of the tarsus, and is the 

 longest of the tarsal ligaments. Further, it forms the greater 

 part of the sheath of the tendon of the peronaeus longus. 



The plantar calcaneo-cuboid ligament (O.T. short plantar 

 ligament} is placed under cover of the long plantar ligament. 

 Slip the knife between them and carry the cutting edge back- 

 wards so as to detach the long plantar ligament from the 

 plantar surface of the calcaneus. When the detached band is 

 thrown forwards the plantar calcaneo-cuboid ligament comes 

 into view, and little dissection is required to make its connec- 

 tions apparent. It is composed of short, strong fibres, not 

 more than an inch in length. They spring from the small 

 tubercle on the anterior part of the plantar surface of the 

 calcaneus, and are attached, anteriorly, to the plantar surface 

 of the cuboid, posterior to its tuberosity. The ligament is 

 broader than the long plantar ligament and could be seen 

 at the medial border of the latter before it was reflected. 



In the maintenance of the longitudinal arch of the foot, 



