THE FIBULA. 297 



tibial band. In front of the upper end of the bone, between the tuberosities, is the tubercle of 

 the tibia, fonnine: an oval eminence, which is continuous below with the anterior border or crest 

 of the bone. This bonier can be felt, forming the prominence of the shin, in the upper two- 

 thirds of its extent being sharp and presenting a somewhat flexuous course, being curved out- 

 ward above and inward below. In the lower third of the leg the border disappears, and the 

 bone is concealed by the tendons of the muscles on the front of the leg. Internal to the ante- 

 rior border is to be felt the broad internal surface of the tibja, slightly encroached upon by the 

 muscles in front and behind. It commences above at the wide expanded inner tuberosity, and 

 terminates below at the internal malleolus. The internal malleolus is a broad prominence situ- 

 ated on a higher level and somewhat farther forward than the external malleolus. It overhangs 

 the inner border of the arch of the foot. Its anterior border is nearly straight; its posterior 

 border presents a sharp edge, which forms the inner margin of the groove for the tendon of 

 the Tibialis posticus muscle. 



The Fibula (Figs. 220, 221). 



The Fibula (iibnl<t. a clasp) is situated at the outer side of the leg. It is the 

 smaller of the two bones, and, in proportion to its length, the most slender of all 

 the long bones : it is placed nearly parallel but behind the level of the tibia. Its 

 upper extremity is small, placed toward the back of the head of the tibia and 

 below the level of the knee-joint, and excluded from its formation ; the lower 

 extremity inclines a little forward, so as to be on a plane anterior to that of the 

 upper end, projects below the tibia, and forms the outer ankle. It presents for 

 examination a shaft and two extremities. 



The Upper Extremity, or Head, is of an irregular quadrate form, presenting 

 above a flattened articular facet, directed upward, forward, and inward, for artic- 

 ulation with a corresponding facet on the external tuberosity of the tibia. On 

 the outer side is a thick and rough prominence, continued behind into a pointed 

 eminence, the styloid process* which projects upward from the posterior part of 

 the head. The prominence gives attachment to the tendon of the Biceps muscle 

 and to the long external lateral ligament of the knee, the ligament dividing the 

 tendon into two parts. The summit of the styloid process gives attachment to the 

 short external lateral ligament. The remaining part of the circumference of the 

 head is rough, for the attachment of the anterior superior tibio-fibular ligament, 

 presenting, in front, a tubercle for the attachment of the upper and anterior part 

 of the Peroneus longus ; and behind, another tubercle for the attachment of the 

 posterior superior tibio-fibular ligament and the upper fibres of the Soleus muscle. 



The shaft presents four borders the antero-external, the antero-internal, the 

 postero-external. and the postero-internal ; and four surfaces anterior, posterior, 

 internal, and external. 



The antero-external border commences above in front of the head, runs verti- 

 cally downward to a little below the middle of the bone, and then, curving some- 

 what outward, bifurcates so as to embrace the triangular subcutaneous surface 

 immediately above the outer surface of the external malleolus. This border gives 

 attachment to an intermuscular septum, which separates the extensor muscles on 

 the anterior surface of the leg from the Peroneus longus and brevis muscles. 



The antero-internal border, or interosseous ridge, is situated close to the inner 

 si<le of the preceding, and runs nearly parallel with it in the upper third of its 

 extent, but diverges from it so a? co include a broader space in the lower two-thirds. 

 It commences above just beneath the head of the bone (sometimes it is quite 

 indistinct for about an inch below the head), and terminates below* at the apex of 

 a rough triangular surface immediately above the articular facet of the external 

 malleolus. It serves for the attachment of the interosseous membrane, and sepa- 

 rates the extensor muscles in front from the flexor muscles behind. 



The postero-external border is prominent; it commences above at the base 

 of the styloid process, and terminates below in the posterior border of the outer 

 malleolus. It is directed outward above, backward in the middle of its course, 

 backward and a little inward below, and gives attachment to an aponeurosis 

 which separates the Peronei muscles on the outer surface of the shaft from the 

 flex >r muscles on its posterior surface. 



