THE BONES OF THE LOWER LIMB 



343 



fibula are on the same horizontal plane above and below, but 

 over about the middle three-fifths the fibula projects slightly 

 farther back on account of its cur\'e. Anteriorly the tibia is on 

 a more anterior plane than the fibula, a point to be borne in 

 mind in making flaps by transfixion. The tibia is a long bone, 

 and is divisible into a shaft and two extremities, upper and 

 lower. 



The upper extremity, known as the head, is broader from side 

 to side than from before backwards. Antero-laterally it is convex, 

 but posteriorly it is rendered concave by the popliteal notch at its 

 centre. The enlargements of the bone on either side of the head 

 are called the tuberosities, external and internal. The external 

 tuberosity is rather smaller than the internal, and at its posterior 

 and under aspect it presents a flat circular facet, directed downwards. 



Anterior Comu of Internal 



Fibro-Cartilage Tuberde 



Anterior Cmcial Ligament *' 



Intemal 

 Condylar Surfac-: 



Anterior Comu of External 

 Fibro-Cartilage 



External Tabeick at Spine 



External Condylar 

 Stirface 



Intemal Tubercle of Spint- 

 Posterior Coma of Intemal Fibro-Cartilage i Popliteal Notch 



Posterior Crucial Ligament 



Posterior Comu of External 



Fibro-Cartfl age 



Fig. 143 The Head of the Right Tibia (Superior View). 



backwards, and outwards, which articulates with the head of the 

 fibula. The cartilage of this facet is occasionally continuous with 

 that of the external condylar surface. At the junction of its 

 anterior and outer surfaces the external tuberosity presents an 

 elevation, which usually assumes the form of a ridge, for the 

 attachment of the ilio-tibial band of the fascia lata. The internal 

 tuber nsiiy is larger than the external, and has a distinct inclina- 

 tion backi^'ards as well as inwards, a point to be noted in setting 

 fractures of this bone. On its posterior aspect it presents a hori- 

 zontal groove for the insertion of the chief portion of the tendon 

 of the semimembranosus muscle. On the anterior aspect of the 

 superior extremity, at the junction of the head and shaft, there is a 

 well-marked projection, called the tubercle or anterior tuberosity. 

 It is fully I inch in length, and its upper border is about | inch 



