remaining part of the posterior surface is smooth and covered by the Tibialis 

 posterior, Flexor digitorum longus, and Flexor hallucis longus. Immediately below 

 the popliteal line is the nutrient foramen, which is large and directed obliquely 

 downward. 



The Lower Extremity (distal extremity). The lower extremity, much smaller 

 than the upper, presents five surfaces; it is prolonged downward on its medial 

 side as a strong process, the medial malleolus. 



Surfaces. The inferior articular surface is quadrilateral, and smooth for articu- 

 lation with the talus. It is concave from before backward, broader in front than 

 behind, and traversed from before backward by a slight elevation, separating 

 two depressions. It is continuous with that on the medial malleolus. 



Upper extremity 



Appears before or 

 shortly after birth 



Appears at 2nd 

 year 



Joins body 

 'about 20th year 



Joins body about 

 18th year 



Lower extremity 



Flo. 260. Plan of ossification of the tibia. From three 

 centers. 



FIG. 261. Epiphysial lines of tibia and fibula 

 in a young adult. Anterior aspect. 



The anterior surface of the lower extremity is smooth and rounded above, and 

 covered by the tendons of the Extensor muscles; its lower margin presents a rough 

 transverse depression for the attachment of the articular capsule of the ankle- 

 joint. 



The posterior surface is traversed by a shallow groove directed obliquely down- 

 ward and medialward, continuous with a similar groove on the posterior surface 

 of the talus and serving for the passage of the tendon of the Flexor hallucis longus. 



The lateral surface presents a triangular rough depression for the attachment 

 of the inferior interosseous ligament connecting it with the fibula; the lower part 

 of this depression is smooth, covered with cartilage in the fresh state, and articu- 

 lates with the fibula. The surface is bounded by two prominent borders, con- 

 tinuous above with the interosseous crest; they afford attachment to the anterior 

 and posterior ligaments of the lateral malleolus. 



The medial surface is prolonged downward to form a strong pyramidal process, 

 flattened from without inward the medial malleolus. The medial surface of this 

 process is convex and subcutaneous; its lateral or articular surface is smooth and 

 lightly concave, and articulates with the talus; its anterior border is rough, for 



