582 A MANUAL OF ANATOMY 



III. Calcaneo-cuboid Joint. — This belongs to the class diar- 

 throsis, and to the subdivision reciprocal or saddle-joint. The liga- 

 ments are dorsal, internal or interosseous, long plantar, and short 

 plantar. 



The dorsdJ ligament is a broad, flat band which passes between 

 the superior surfaces of the os calcis and cuboid. 



The internal or interosseous ligament is a strong band which 

 lies deeply in the hollow between the fore parts of the astragalus 

 and OS calcis, where it is connected with the external calcaneo- 

 navicular ligament. Its attachments are to the adjacent inner 

 portions of the os calcis and cuboid. 



The long plantar (long inferior calcaneo-cuboid) ligament is very 

 strong, and is attached posteriorly to the plantar surface of the os 

 calcis, upon which it extends from the inner and outer tubercles 

 to the anterior tubercle. Anteriorly most of its fibres are attached 

 to the ridge on the plantar surface of the cuboid bone behind the 

 peroneal groove. Some of them, however, are continued forwards to 

 be attached to the plantar aspects of the bases of the second, third, 

 fourth, and fifth metatarsal bones. These latter fibres, as they 

 pass over the peroneal groove, cover the tendon of the peroneus 

 longus, and so complete its fibro-osseous canal. 



The short plantar (short inferior calcaneo-cuboid) ligament is more 

 deeply placed than the preceding. Posteriorly it is attached to the 

 plantar surface of the os calcis in front of the anterior tubercle, as 

 well as to the fore part of that tubercle, and anteriorly to the 

 plantar surface of the cuboid bone behind the ridge. 



The long and short plantar ligaments are in early life continuous with 

 the tendo Achillis, but they become subsequently separated from it as the 

 result of the backward growth of the heel. 



The synovial membrane of this joint is peculiar to it. 



Arterial Supply. — ^The external tarsal branch of the dorsalis pedis 

 and the external plantar artery. 



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

 the dorsalis pedis nerve. 



Movements at the Astragalo-navicular and Calcaneo-cuboid Joints.— The 



movements at these joints are flexion and extension, combined with abduction, 

 adduction, and rotation. Flexion occurs during extension of the ankle-joint, 

 and extension during flexion of that joint. The axis of these movements 

 passes from the inner side of the neck of the astragalus obliquely down- 

 wards, outwards, and backwards to the lower and outer part of the tuber 

 calcis. During flexion and extension of the astragalo-navicular joint rota- 

 tion of the navicular bone on the head of the astragalus takes place. The 

 most free movement at this joint is downwards and inwards, or upwards 

 and outwards. In adduction and abduction of the foot movement takes 

 place at this joint as well as at the astragalo-calcaneal articulations. In 

 adduction or inversion the navicular bone moves downwards and inwards, 

 and so also does the cuboid at the calcaneo-cuboid joint, the result being 

 that the antero-posterior arch of the foot is diminished. In abduction or 

 eversion the navicular and cuboid bones move upwards and outwards, and 

 the antero-posterior arch is increased. 



In walking the head of the astragalus tends to sink upon the spring ligament, 



