156 THE SKELETON 



The internal latrral ligament is attached to its upix-r 7o em. (3"), and the middle 

 third jiive-s origin to the >ioleii.s. The interosseous border extends from the tibular 

 facet on the outer tuberosity to the lower end of the bone; towards its termination 

 the l>order bifurcates to enclose a triangular space for the attachment of the inter- 

 osseous ligament between the tibia and lilnila. The part above the bifurcation is 

 connected with the interosseous membrane. 



These borders limit three surfaces. The internal surface is Ijounded by the 

 internal l)order and the crest; it is broad above, where it receives the insertion of 

 the sartorim, gracilii, and .'<emiteii(liiwsus ; the rest of the surface is convex and 

 subcutaneous. The external surface lies between the crest of the tibia and the 

 interosseous l)order. The u\)\)ev two-thirds presents a hollow for the origin of 

 the tibialis anticKs; the rest of the surface is overlaid by the extensor tendons and 

 the anterior tibial vessels. The posterior surface is limited by the interosseous 

 ridge and the internal border. The upper part presents a rough oblique ridge, 

 extending from the tibular facet on the outer tuberosity to the internal ])order, a 

 little above the middle of the bone. This oblique ridge gives origin to the soleu.-> 

 and attachment to the popliteal fascia; the surface above is for the insertion of the 

 poplitens. An indefinite vertical ridge commences near the middle of the oblique 

 line, and marks off a semilunar space, limited externally by the interosseous border. 

 This is for the tibialis 2:>osticus ; it extends as low as the junction of the middle and 

 lower thirds. The portion of bone inside this vertical line is for the flexor longus 

 digitorum. The loAver third of the posterior surface is covered by flexor tendons. 



The inferior extremity is somewhat quadrilateral, and reseml)les the distal end 

 of the radius. Its inferior surface is articular for the upper surface of the astraga- 

 lus and is continuous with the external surface of the malleolus, which articulates 

 Avith the facet on the inner side of the astragalus. The outer surface has a triangular 

 rough area for the lower end of the shaft of the fibula, its margins being rough for 

 ligaments. The anterior border is slightly convex, and by its margin gives attach- 

 ment to the anterior ligament of the ankle. The posterior surface has two grooves: 

 the one which encroaches on the malleolus is for the tendons of tibialis jMsticus 

 and flexor longus digitorum, and an outer shallow^ groove for the tendon of flexor 

 longus halbfcis. The inner surface is prolonged downwards to form the malleolus ; 

 from its tip and margins the internal lateral (deltoid) ligament of the ankle-joint 

 arises. The inner surface of the malleolus is convex and subcutaneous; the outer, 

 as already stated, has a facet for the inner surface of the astragalus. 



The ti1)ia affords attachment to the following muscles : — 



Semimembranosus. Tibialis posticus. 



Sartorius. Tibialis anticus. 



Gracilis. Soleus. 



Semitendinosus. Peroneus longus. 



Quadriceps extensor. Flexor longus digitorum. 



Popliteus. Extensor longus digitorum. 

 Tensor vaginse femoris (indirectly). Bicej^s femoris. 



Ligaments : — 



Anterior crucial. Coronary. 



Posterior crucial. Anterior tiljio-fibular (superior). 



Internal lateral of the knee. Posterior tibio-fibular (superior). 



Internal semilunar cartilage. Ilio-tibial band. 



External semilunar cartilag(\ Interosseous membrane. 



Anterior tibio-lil)ular (inferior). Anterior annular (oblique). 



Posterior tibio-fibular ^inferior). Internal annular. 



Anterior of ankle. Internal lateral of ankle (deltoid). 



Anterior annular (transverse). Posterior (of ankle). 



Transverse. 



Blood-supply.— The tibia is a very vascular bone. The nutrient arterv for the 

 shaft is furnished I >y tiie posterior tibial; it enters the bone near the interosseous 



