554 



APPLIED ANATOMY. 



front of it to be inserted into the prominent tuberosity of the fifth metatarsal bone. 

 The long tendon passes behind the tubercle, winds around the cuboid, and crosses 

 the sole to insert into the internal cuneiform and base of the first metatarsal bone. 



Posteriorly the tendo calcaneus (Achillis) is large and prominent along the 

 anterior edge of its lateral (external) side run the external (short.) saphenous vein 

 and nerve. Running upward from the posterior border of the internal malleolus the 

 tibialis posterior tendon can sometimes be seen and felt. Posterior to it runs the 

 flexor longus digitorum muscle, then the posterior tibial artery, accompanied by 

 venae comites, then the posterior tibial nerve, and lastly the flexor longus hallucis. 

 The artery can be felt pulsating midway between the tendo calcaneus and the 

 internal tuberosity of the calcaneum. The anterior tibial artery can be felt pulsat- 

 ing to the lateral (outer) side of the flexor longus hallucis. 



THE ANKLE-JOINT. 



Ligaments and Movements. The ankle-joint is a pure hinge-joint and its 

 motion is anteroposterior except in complete extension, when a small amount of 



lateral movement is possible. The range of move- 

 ment is 80 degrees; 20 degrees flexion, and 60 de- 

 grees extension. 



The tibia and fibula above articulate with the 

 surface of the body of the astragalus below. The 

 articular facet for the fibula is about twice as long 

 from above downward as is that for the internal 

 malleolus. The hollow below the internal malleolus 

 is filled by the internal lateral ligament and the ten- 

 don of the tibialis posterior. The inferior tibio- 

 fibular joint is sometimes practically lacking, there 

 being almost no continuation of the ankle-joint up 

 between the tibia and fibula. The junction of these 

 two bones is very strong, the ligaments being an 

 anterior, posterior, interosseous, and a transverse 

 inferior tibiofibular ligament which passes across the 

 back of the ankle-joint reinforcing the posterior por- 

 tion of the capsular ligament. The upper surface 

 of the astragalus is one-fourth wider in front than 

 behind, so that in extension it is not so firmly locked 

 between the malleoli as in flexion (Fig. 568). Its 

 upper surface is slightly concave. Flexion and 

 extension take place on a transverse axis passing 

 through the body of the astragalus at the tip of the 

 external malleolus. This axis is not exactly trans- 

 verse but is slightly oblique, so that on extension 

 the foot is pointed slightly outward. The ankle 

 has a capsular ligament which is very thin in front 

 and behind the joint. Posteriorly it is reinforced 

 above by the transverse inferior tibiofibular liga- 

 ment. The flexor longus hallucis also supports it 

 posteriorly. The internal and external lateral liga- 

 ments are strong, the internal being the stronger. 

 The internal lateral or ligamentum deltoideum 

 runs from the malleolus above to the scaphoid, astragalus, and calcaneum below. 

 It is crossed on its surface by the tendons of the tibialis posterior and flexor longus 

 digitorum muscles (Fig. 569). 



The external lateral ligament has three fasciculi : an anterior one to the astrag- 

 alus; a middle one to the side of the calcaneum, and a posterior one to the posterior 

 part of the astragalus (Fig. 570). In both extreme flexion and extension the edges 

 of the tibia come in contact with the astragalus and hence limit further movement. 

 The ligaments also aid in restricting motion. 



FIG. 508. The upper articular sur- 

 face of the astragalus, showing it to be 

 slightly concave and one fourth wider in 

 front than behind. 



