234 SPECIAL ANATOMY OF THE SKELETON 



and outward, for articulation with the fibula. Its lateral surface is convex and 

 rough, more prominent in front than the internal, and presents a prominent 

 rough eminence, situated on a level with the upper border of the tubercle of the 

 tibia at the junction of its anterior and outer surfaces, for the attachment of the 

 iliotibial band. Just below this the Extensor longus digitorum arises, and a slip 

 from the Biceps femoris cruris is attached. 



Shaft of the Tibia (corpus tibiae}. The shaft of the tibia is of a triangular 

 prismoid form, broad above, gradually decreasing in size to its most slender part, 

 the commencement of its lower fourth; it then enlarges again toward its lower 

 extremity. It presents for examination three borders and three surfaces. 



The anterior border, the most prominent, is called the crest of the tibia (crista 

 anterior}; it commences above at the tubercle, and terminates below at the anterior 

 margin of the inner malleolus. This border is very prominent in the upper 

 two-thirds of its extent, smooth and rounded below. It presents a very sinuous 

 course, being usually curved outward above and inward below; it gives attachment 

 to the deep fascia of the leg. 



The internal border (margo medialis) is smooth and rounded above and below, 

 but more prominent in the centre; it commences at the back part of the inner tuber- 

 osity, and terminates at the posterior border of the internal malleolus; its upper 

 part gives attachment to the internal lateral ligament of the knee to the extent 

 of about two inches, and to some fibres of the Popliteus muscle, and its middle 

 third to some fibres of origin of the Soleus and Flexor longus digitorum muscles 



The external border (crista interossed), or interosseous ridge, is thin and prominent, 

 especially its central part, and gives attachment to the interosseous membrane; 

 it commences above in front of the fibular articular facet, and bifurcates below, 

 to form the boundaries of a triangular rough surface, for the attachment of the 

 interosseous ligament connecting the tibia and fibula. 



The internal surface (fades medialis} is smooth, convex, and broader above than 

 below; its upper third, directed forward and inward, is covered by the aponeurosis 

 derived from the tendon of the Sartorius, and by the tendons of the Gracilis and 

 Semitendinosus, all of which are inserted nearly as far forward as the anterior 

 border; in the rest of its extent it is subcutaneous. 



The external surface (Jades lateralis) is narrower than the internal; its upper 

 two-thirds presents a shallow groove for the origin of the Tibialis anticus muscle; 

 its lower third is smooth, convex, curves gradually forward to the anterior aspect 

 of the bone, and is covered from within outward by the tendons of the following 

 muscles: Tibialis anticus, Extensor proprius hallucis, Extensor longus digitorum. 



The posterior surface (fades posterior} (Fig. 186) presents, at its upper part, a 

 prominent ridge, the oblique line of the tibia (linea poplitea), which extends from 

 the back part of the articular facet for the fibula obliquely downward, to the in- 

 ternal border, at the junction of its upper and middle thirds. It marks the lower 

 limit for the insertion of the Popliteus muscle, and serves for rfie attachment of 

 the popliteal fascia and part of the Soleus, Flexor longus digitorum, and Tibialis 

 posticus muscles; the triangular concave surface, above and to the inner side of 

 this line, gives attachment to the Popliteus muscle. The middle third of the 

 posterior surface is divided by a vertical ridge into two lateral halves; the ridge 

 is well marked at its commencement at the oblique line, but becomes gradually 

 indistinct below; the inner and broader half gives origin to the Flexor longus 

 digitorum, the outer and narrower to part of the Tibialis posticus. The remaining 

 part of the bone presents a smooth surface covered by the Tibialis posticus, 

 Flexor longus digitorum, and Flexor longus hallucis muscles. Immediately 

 below the oblique line is the nutrient foramen, which is large and directed obliquely 

 downward. It is the opening of the nutrient canal, which is directed toward the 

 ankle. 



