THE TIBIA 6i 



four-sided. It is smooth and upon it the flexor perforans muscle 

 lies. 



Three edges separate the surfaces which we have described above. 

 In the upper third of the bone the anterior edge stands out prominently 

 and is sharp and well defined. This portion constitutes what is known 

 as the crest of the tibia. For the remainder of its extent this edge is ill- 

 defined. 



The outer edge is concave in the longitudinal direction, and slightly 

 convex transversely. This edge forms with the deep face of the fibula, 

 the tibio-fibular arch, through the upper portion of which the anterior 

 tibial vessels pass, leaving a well-marked vascular impression on the 

 tibia. 



The inner edge is almost straight. In the upper third of this 

 edge there will be observed a well-defined tubercle, to which the popliteus 

 muscle is attached. 



The superior extremity of the tibia is very massive, and is made up 

 of three tuberosities, the tibial spine, and a non-articular, roughened area, 

 which serves for the attachment of ligaments. One of the tuberosities 

 is placed mesially in front, and the remaining two alongside one another 

 posteriorly. 



The anterior tuberosity is roughened and non-articular. Inferiorly 

 it is continuous with the crest of the tibia. This tuberosity is divided 

 into two parts by a well-marked groove, which is disposed vertically. 

 That portion to the outer side of the groove is much the more prominent. 

 It extends to the higher level, and outwardly it projects over the notch 

 through which the common tendon of the extensor pedis muscle and super- 

 ficial division of the flexor metatarsi plays. Anteriorly this portion is 

 roughened, and it gives attachment to the external straight ligament of 

 the patella. The portion of the anterior tuberosity to the inner side of 

 the groove is much less pronounced, and inwardly it passes insensibly 

 into the roughened border of the internal tuberosity. Anteriorly this 

 portion is also roughened, and to it the internal straight ligament of the 



