57<5 A MANUAL OF ANATOMY 



almost fully extended, if the fingers are placed over the head of the fibula whilst 

 the foot is alternately flexed and extended, the head of the bone will be felt 

 to glide upwards during flexion and downwards during extension of the foot. 



Inferior Tibio-fibular Joint. — This joint belongs to the class 

 diarthrosis, and to the subdivision arthrodia. The articular sur- 

 faces are the upper part of the facet on the inner surface of the 

 external malleolus of the fibula and the sigmoid cavity on the 

 outer aspect of the lower end of the tibia. The ligaments are an- 

 terior, posterior, inferior interosseous, and transverse. 



The anterior ligament is a strong, fiat band, the fibres of which 

 pass obliquely downwards and outwards from the tibia to the fibula. 

 It is related anteriorly to the peroneus tertius, and posteriorly is 

 in contact with the inferior interosseous ligament. 



The posterior ligament, which is disposed like the anterior, is 

 in contact with the transverse ligament inferiorly, and with the 

 inferior interosseous ligament anteriorly. 



The inferior interosseous ligament is an important ligament, 

 and is of considerable strength. It consists of short fibres which 

 pass directly between the opposed rough triangular surfaces at the 

 lower ends of the shafts of the tibia and fibula. It is continuous 

 above with the interosseous membrane, and its extent is about 

 i^ inches. Anteriorly and posteriorly it is in part related to the 

 anterior and posterior inferior tibio-fibular ligaments. The part 

 of the inferior tibio-fibular joint occupied by the inferior, inter- 

 osseous ligament belongs to the class amphiarthrosis, and to the 

 subdivision syndesmosis. 



The transverse ligament, which is strong, narrow, and somewhat 

 round, extends almost horizontally from the posterior border of 

 the lower end of the tibia to the upper part of the digital fossa 

 of the external malleolus. Externally it lies along the lower border 

 of the posterior inferior tibio-fibular ligament, by which it is 

 slightly overlapped. It fills up a slight hollow between the tibia 

 and fibula, and it plays across the back part of the upper articular 

 surface of the astragalus, where it usually gives rise to a transverse 

 groove. The transverse ligament completes the back part of the 

 tibial socket for the upper surface of the astragalus. 



The synovial membrane is continuous with that of the ankle- 

 joint. 



Arterial Supply. — The posterior and anterior peroneal arteries, 

 and the external malleolar of the anterior tibial. 



Nerve-supply. — The interosseous branch of the nerve to the pop- 

 liteus muscle, and the external division of the dorsalis pedis nerve. 



Movements. — These are very limited, and are of a gliding nature, chiefly 

 upwards and downwards, the fibula moving on the tibia. Though the bones 

 are firmly bound together by the inferior interosseous ligament, there is yet a 

 certain amount of lateral separation allowed during flexion of the foot. 



Intermediate Connection between the Tibia and Fibula. — The 



union between the shafts of the tibia and fibula is effected by 



