390 HUMAN ANATOMY. 



Post-typhoidal periostitis and osteitis of the tibia are exceedingly common, and 

 affect particularly the subcutaneous area of the bone near the lower third, where 

 there are no muscular attachments. They are probably due, therefore, to slight 

 traumatisms. This same area is peculiarly subject not only to this form of infection 

 and, as has been said, to fracture, but also to tuberculosis (when the epiphyses are 

 spared), to syphilitic nodes and gummata, to softening and deformity from rickets, 

 and to sepsis spreading inward from cutaneous inflammations and ulcers. It is 

 probably so vulnerable by reason of its exposure to frequent slight injury and to 

 strain disproportionate to its size and strength {vide supra), and because of its 

 dependent position and its distance from the main source of the blood-supply of the 

 bone (the nutrient artery entering it at its upper third), both of which circumstances 

 favor passive hyperaemia and the localization of infection. 



Sarcoma, in accordance with the general rule already mentioned (page 366), 

 affects chiefly the upper third of the tibia. 



Landmarks. — On the inner side of the knee the internal tuberosity of the 

 tibia is in close relation in extension with the internal condyle of the femur, the two 

 making a uniform rounded prominence. The interval between them can be felt 

 but not seen. If the leg is flexed and the ankle rested upon the opposite knee, the 

 tibial tuberosity becomes visible and lies in advance of the inner condyle. The 

 prominence of the outer tuberosity is distinctly to be seen and felt on the antero- 

 external aspect of the limb about 2.5 centimetres (one inch) below the joint-line. 

 It represents the lowest level of the synovial membrane. Into it is inserted, about 

 half-way between the tip of the patella and the head of the fibula, the important 

 ilio-tibial band of fascia to which illusion has been made in reference to fracture of 

 the neck of the femur and dislocation of the hip (page 377). 



The posterior edge of the head of the tibia is not accessible to direct examina- 

 tion, and this is true of the external and posterior surfaces throughout. 



The internal border can be traced from the tuberosity to the malleolus. The 

 antero-internal surface, which is subcutaneous throughout, can be seen and felt. 

 The anterior border or crest constitutes the prominence of the "shin." It is 

 sharp in the upper two-thirds and fades into the shaft at the summit of the lower 

 third. In well-marked tibiae it presents a distinct double curve, the upper part of 

 which has its concavity outward. The tubercle is easily felt and seen. It should 

 be in line with the ligamentum patellae and a point on the front of the ankle mid- 

 way between the malleoli. It is about on a level with the head of the fibula. 



The inner malleolus is twelve millimetres (half an inch) above and in front of 

 the outer malleolus, but on the same plane posteriorly. Its lower border is rounded. 

 The notch for the internal lateral ligament can be felt. Its tip is twelve millimetres 

 below the joint-line. Its sharp posterior border forms the inner boundary of the 

 groove for the tibialis posticus tendon. 



THE FIBULA. 



The fibula is a long, slender bone with a knob-like upper end and a pointed 

 lower one. 



The upper extremity, called the head,^ has a rounded or^ vaguely quadri- 

 lateral articular surface above, looking upward, a little inward and forward, to 

 meet the corresponding one on the tibia. The styloid process, ^ a short prominence, 

 juts upward from its outer posterior angle. The outer part of the head is rough. 

 An ill-marked neck below it is indistinguishable from the shaft. 



The shaft ^ is best described as having four borders, separating four sides, though 

 one of the borders joins another near the lower end. The borders, proceeding in 

 regular order round the bone from the front, are (i) the antero-external, (2) the 

 postero-external, (3) the postero-internal, sometimes called the <?^/z^?^^ r/^^, and (4) 

 the antero-internal or interosseous. The antero-exter^ial border begins faintly on the 

 front of the shaft, a little below the neck, and becomes very prominent as it descends, 

 twisting slightly outward. In the last quarter it splits into two lines which run to 

 the front and back of the outer malleolus, enclosing a triangular subcutaneous space. 

 The postero-external border begins on the outer side of the neck below the styloid 



^ Capitulam fibulae. ~ Apex capituli fibulae. ^ Corpus fibulae. 



