574 A MANUAL OF ANATOMY 



The synovial or tendon-sheaths around the ankle-joint are very 

 numerous and of great importance. In all there are nine sheaths, 

 three of which are in front of the ankle-joint, three behind the 

 internal malleolus between it and the tuber calcis, one behind the 

 external malleolus, and two on the outer surface of the os calcis. 



The anterior tendon-sheaths, from within outwards, are as 

 follows : 



Sheath of tendon of tibiahs anticus. 

 Sheath of tendon of extensor longus hallucis. 

 Sheath of tendons of extensor longus digitorum and 

 peroneus tertius. 



These sheaths, which have no communication with the ankle- 

 joint, frequently become the seat of teno-vaginitis or tenosynovitis. 



The sheath of the tendon of the tibialis anticus Hke the tendon 

 which it invests, passes through a special compartment in the 

 superior division of the anterior annular ligament, which lies just 

 above the ankle-joint, through a special compartment in the upper 

 band of the inferior division of that ligament, and beneath its 

 lower band, the inferior division of the ligament being placed just 

 in front of the ankle-joint. It is the only synovial sheath within 

 the superior division, and it ceases beneath the lower band of the 

 inferior division, on a level with the scaphoid or navicular bone. 



The sheath of the tendon of the extensor longus hallucis only 

 invests that tendon as it passes through a special compartment in 

 the upper band of the inferior division of the anterior annular liga- 

 ment. It is not present beneath the superior division of the liga- 

 ment. It commences just above the upper band of the inferior 

 division of the ligament, and it terminates about the level of the 

 joint between the internal cuneiform and first metatarsal bone. 



The common sheath of the tendons of the extensor longus digi- 

 torum and peroneus tertius only invests these tendons as they pass 

 through a special compartment in the outer single portion (fundi- 

 form ligament of Retzius) of the inferior division of the anterior 

 annular ligament. It is not present beneath the superior division 

 of the ligament. It commences a little above the fundi,form liga- 

 ment of Retzius, and it terminates about the level of the front part 

 of the cuboid bone. 



The internal malleolar tendon-sheaths are situated between the 

 posterior part^f the internal malleolus and the tuber calcis. They 

 are three in number, and are quite independent of one another. 

 The tendons to which they belong are (i) the tendon of the tibialis 

 posticus, (2) the tendon of the flexor longus digitorum, and (3) the 

 tendon of the flexor longus hallucis. All three sheaths lie beneath 

 the internal annular ligament, which extends between the posterior 

 border of the internal malleolus and the internal border of the tuber 

 calcis. They commence about 2 inches above that ligament, and 

 extend forwards beyond it for about 2 inches in advance of the 

 internal malleolus. These three sheaths are frequently the seat of 

 tenosynovitis. 



