5 66 



APPLIED ANATOMY. 



When the weight of the body is transmitted to the foot it tends to flatten the 

 anteroposterior arch. If the arch descends it can only do so either by pushing 

 the astragalus up luxating it or by the ligaments of the arch stretching or ruptur- 

 ing and allowing the two pillars of the arch to separate. In disease the ligaments 

 elongate and by violence they may be ruptured, the arch in each case falls. If 

 the ligaments supporting the astragalus remain intact then excessive lateral move- 

 ment ruptures those on the side and a sprain of the subastragaloid joint is produced 

 which is often called a sprain of the ankle. 



The Midtarsal Joint (Chopart's Joint). This is composed anteriorly of 

 the scaphoid and cuboid bones and posteriorly by the astragalus and os calcis. The 

 movements are not extensive and consist of flexion with inward rotation of the sole, 

 and extension with outward rotation of the sole. The joint is separated into an inner 

 and outer portion by an interosseous ligament where the cuboid, astragalus, and os 

 calcis meet. 



The Ligamentous Support of the Arch of the Foot. The bony con- 

 struction of the arch or dome of the foot has already been explained (page 563). The 



Long plantar ligament 



Short plantar ligament 



Peroneus longus 

 Peroneus brevis 



- Groove for flexor longus hallucis 



Groove for posterior tibial and flexor 

 communis digitorum 



Inferior calcaneoscaphoid ligament 

 Posterior tibial tendon 



FIG. 585. Ligaments and tendons of the sole of the foot. 



various bones composing it are bound together not only by the short ligaments pass- 

 ing between contiguous bones, but the arch is strengthened by three special ligamen- 

 tous structures. They are the inferior calcaneoscaphoid ligament, the plantar liga- 

 ments, long and short, and the plantar fascia. 



The inferior calcaneoscaphoid ligament (ligamentum calcaneonaviculare plantar e} 

 runs from the lower inner portion of the scaphoid, posterior to its tubercle, to the sus- 

 tentaculum tali. It is an extremely strong fibrocartilaginous band. Anteriorly and 

 above it blends with the internal lateral ligament (deltoid) of the ankle. Together 

 with the posterior surface of the scaphoid it forms a socket for the head of the 

 astragalus. This ligament fills the long gap left in the inner arch of the foot between 

 the scaphoid and os calcis. Running under and supporting it is the tendon of the 

 tibialis posterior (Fig. 585). 



The long plantar or long calcaneocuboid ligament (ligamentum plantare 

 longum) is attached to the under surface of the os calcis in front of its tubercles 

 and thence runs to the peroneal ridge on the cuboid bone and continues onward to 



