352 SYNDESMOLOGY 



approximation of the dorsum of the foot to the front of the leg, while in extension the heel is 

 drawn up and the toes pointed downward. The range of movement varies in different individuals 

 from about 50 to 90. The transverse axis about which movement takes place is slightly oblique. 

 The malleoli tightly embrace the talus in all positions of the joint, so that any slight degree of 

 side-to-side movement which may exist is simply due to stretching of the ligaments of the talo- 

 fibular syndesmosis, and slight bending of the body of the fibula. The superior articular surface 

 of the talus is broader in front than behind. In dorsiflexion, herefore, greater space is required 

 between the two malleoli. This is obtained by a slight outward rotatory movement of the lower 

 end of the fibula and a stretching of the ligaments of the syndesmosis; this lateral movement is 

 facilitated by a slight gliding at the tibiofibular articulation, and possibly also by the bending of 

 the body of the fibula. Of the ligaments, the deltoid is of very great power so much so, that 

 it usually resists a force which fractures the process of bone to which it is attached. Its middle 

 portion, together with the calcaneofibular ligament, binds the bones of the leg firmly to the 

 foot, and resists displacement in every direction. Its anterior and posterior fibers limit extension 

 and flexion of the foot respectively, and the anterior fibers also limit abduction. The posterior 

 talofibular ligament assists the calcaneofibular in resisting the displacement of the foot back- 

 ward, and deepens the cavity for the reception of the talus. The anterior talofibular is a 

 security against the displacement of the foot forward, and limits extension of the joint. 



The movements of inversion and eversion of the foot, together with the minute changes in 

 form by which it is applied to the ground or takes hold of an object in climbing, etc., are mainly 

 effected in the tarsal joints; the joint which enjoys the greatest amount of motion being that be- 

 tween the talus and calcaneus behind and the navicular and cuboid in front. This is often called 

 the transverse tarsal joint, and it can, with the subordinate joints of the tarsus, replace the ankle- 

 joint in a great measure when the latter has become ankylosed. 



Extension of the foot upon the tibia and fibula is produced by the Gastrocnemius, Soleus, 

 Plantaris, Tibialis posterior, Peronsei longus and brevis, Flexor digitorum longus, and Flexor 

 hallucis longus; dorsiflexion, by the Tibialis anterior, Peronaeus tertius, Extensor digitorum longus, 

 and Extensor hallucis proprius. 1 



V. Intertarsal Articulations (Articulationes Intertarseae ; Articulations 



of the Tarsus). 



Talocalcaneal Articulation (articulatio talocalcanea; articulation of the calcaneus 

 and astragalus; cakaneo-astragaloid articulation). The articulations between the 

 calcaneus and talus are two in number anterior and posterior. Of these, the 

 anterior forms part of the talocalcaneonavicular joint, and will be described with 

 that articulation. The posterior or talocalcaneal articulation is formed between 

 the posterior calcaneal facet on the inferior surface of the talus, and the posterior 

 facet on the superior surface of the calcaneus. It is an arthrodial joint, and the 

 two bones are connected by an articular capsule and by anterior, posterior, lateral , 

 medial, and interosseous talocalcaneal ligaments. 



The Articular Capsule (capsula articularis} . The articular capsule envelops 

 the joint, and consists for the most part of short fibers, which are split up into 

 distinct slips; between these there is only a weak fibrous investment. 



The Anterior Talocalcaneal Ligament (ligamentum talocalcaneum anterius; anterior 

 cakaneo-astragaloid ligament} (Figs. 356, 359). The anterior talocalcaneal liga- 

 ment extends from the front and lateral surface of the neck of the talus to 

 the superior surface of the calcaneus. It forms the posterior boundary of the 

 talocalcaneonavicular joint, and is sometimes described as the anterior interosseous 

 ligament. 



The Posterior Talocalcaneal Ligament (ligamentum talocalcaneum posterius; 

 posterior cakaneo-astragaloid ligament) (Fig. 354). The posterior talocalcaneal 

 ligament connects the lateral tubercle of the talus with the upper and medial part 

 of the calcaneus; it is a short band, and its fibers radiate from their narrow attach- 

 ment to the talus. 



The Lateral Talocalcaneal Ligament (ligamentum talocalcaneum laterale; external 

 cakaneo-astragaloid ligament) (Figs. 356, 359). The lateral talocalcaneal ligament 



i The student must bear in mind that the Extensor digitorum longus and Extensor hallucis proprius are extensors 

 of the toes, but flexors of the ankle; and that the Flexor digitorum longus and Flexor hallucis longus are flexors of the 

 toes, but extensors of the ankle 





