154 



TARSAL ARTICULATIONS. 



Fig. 74.* 



The internal lateral or deltoid ligament is a triangular layer of fibres, 

 attached superiorly by its apex to the internal malleolus, and inferiorly 

 by an expanded base to the astragalus, os calcis, and scaphoid bone. 

 Beneath the superficial layer of this ligament is a much stronger and 

 thicker fasciculus which connects the apex of the internal malleolus 

 with the side of the astragalus. 



This internal lateral ligament is covered in and partly concealed by 

 the tendon of the tibialis posticus, and at its posterior part is in rela- 

 tion with the tendon of the flexor longus digitorum, and with that of 

 the flexor longus pollicis. 



The external lateral ligament consists of three strong fasciculi, which 

 proceed from the inner side of the external malleolus, and diverge in 

 three different directions. The anterior fasciculus passes forwards, 

 and is attached to the astragalus ; the posterior, backwards, and 

 is connected with the astragalus posteriorly ; and the middle, longer 

 than the other two, descends to be inserted into the outer side of the 

 os calcis. 



" It is the strong union of this bone," says Sir Astley Cooper, 

 with the tarsal bones by means of the external lateral ligaments, 

 " which leads to its being more frequently fractured than dis- 

 located." 



The transverse ligament of the 

 tibia and fibula occupies the place 

 of a posterior ligament. It is in 

 relation, behind, with the posterior 

 tibial vessels and nerve, and with 

 the tendon of the tibialis posticus 

 muscle ; and in front, with the ex- 

 tra -synovial adipose tissue, and 

 synovial membrane. 



The Synovial membrane invests 

 the cartilaginous surfaces of the tibia 

 and fibula (sending a duplicature 

 upwards between their lower ends), 

 and the upper surface and two sides 

 of the astragalus. It is then re- 

 flected upon the anterior and lateral 

 ligaments, and upon the transverse 

 ligament posteriorly. 



Actions. The movements of the ankle joint me flexion and extension 

 only, without lateral motion. 



5. Articulation of tlie Tarsal Bones. The ligaments which connect 

 the seven bones of the tarsus to each other are of three kinds, 



* An external view of the ankle joint. 1. The tibia. 2. The external 

 malleolus of the fibula. 3, 3. The astragalus. 4. The os calcis. 5. The cu- 

 boid bone. 6. The anterior fasciculus of the external lateral ligament attached 

 to the astragalus. 7. Its middle fasciculus, attached to the os calcis. 8 Its 

 posterior fasciculus, attached to the astragalus. 9- The anterior ligament of 



