THE TIBIA. 293 



is to say. by violent contraction of the Quadriceps extensor while the limb is in a position of 

 semi-flexion, so that the bone is snapped across the condyles; or by direct violence, such as 

 falls on the knee. In the former class of cases the fracture is transverse ; in the latter it may 

 be oblique, longitudinal, stellate, or the bone variously comminuted. The principal interest in 

 these cases attache.* to their treatment. Owing to the wide separation of the fragments, and 

 the difficulty there is in maintaining them in apposition, union takes place by fibrous tissue, 

 an 1 this may subsequently stretch, producing wide separation of the fragments and permanent 

 lameness. Various plans, including opening the joint and suturing the fragments, have been 

 advocated for overcoming this difficulty. 



In the larger number of cases of fracture of the patella the knee-joint is involved, the car- 

 tilatre which covers its posterior surface being also torn. In some cases of fracture from direct 

 violence, however, this need not necessarily happen, the lesion involving only the superficial 

 part of the bone ; and, as Morris has pointed out. it is an anatomical possibility, in complete 

 fracture, if the lesion involve only the lower and non-articular part of the bone, for it to take 

 place without injury to the synovial membrane. 



The Tibia (Figs. 220, 221). 



The Tibia (tibia, a flute or pipe) is situated at the front and inner side of the 

 leg. and, excepting the femur, is the longest and largest bone in the skeleton. It 

 is prismoid in form, expanded above, where it enters into the knee-joint, more 

 slightly enlarged below. In the male its direction is vertical and parallel with 

 the bone of the opposite side ; but in the female it has a slightly oblique direction 

 downward and outward, to compensate for the oblique direction of the femur 

 inward. It presents for examination a shaft and two extremities. 



The Tipper Extremity, or Head, is large, and expanded on each side into two 

 lateral eminences, the tuberosities. Superiorly, the tuberosities present two smooth, 

 concave surfaces, which articulate with the condyles of the femur ; the internal, 

 articular surface is longer, deeper, and narrower than the external, oval from 

 before backward, to articulate with the internal condyle ; the external one 

 is broader, flatter, and more circular, to articulate with the external condyle. 

 Between the two articular surfaces, and nearer the posterior than the anterior 

 aspect of the bone, is an eminence, the spinous process of the tibia, surmounted 

 by a prominent tubercle on each side, which gives attachment to the extremities 

 of the semilunar fibro-cartilages ; in front and behind the spinous process is a 

 rough depression for the attachment of the anterior and posterior crucial ligaments 

 and the semilunar fibro-cartilages. The anterior surfaces of the tuberosities are 

 continuous with one another, forming a single large surface, which is somewhat 

 flattened : it is triangular, broad above, and perforated by large vascular foramina ; 

 narrow below, where it terminates in a prominent oblong elevation of large size, 

 the tut',-/-.-},- of the tibia : the lower half of this tubercle is rough, for the attachment 

 of the ligament urn patellie ; the upper half presents a smooth facet supporting, 

 in the recent state, a bursa which separates the ligament from the bone. Posteriorly 

 the tuberosities are separated from each other by a shallow depression, the 

 popfit'-'.il notch, which gives attachment to part of the posterior crucial ligament 

 and part of the posterior ligament of the knee-joint. The inner tuberosity presents 

 posteriorly a deep transverse groove, for the insertion of one of the fasciculi of 

 the tendon of the Semi-membranosus, Its lateral surface is convex, rough, and 

 prominent : it gives attachment to the internal lateral ligament. The outer tuber- 

 'jxi.tij presents posteriorly a flat articular facet, nearly circular in form, directed 

 downward, backward, and outward, for articulation with the fibula. Its lateral 

 surface is convex and rough, more prominent in front than the internal : it 

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

 the tubercle of the tibia, for the attachment of the ilio-tibial band. Just below 

 this the Extensor longus digitorum and a slip from the Biceps are attached. 



The Shaft of the tibia is of a triangular prismoid form, broad above, gradually 

 decreasing in size to its most slender part, at the commencement of its lower 

 fourth, where fracture most frequently occurs ; it then enlarges again toward its 

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



The anterior border, the most prominent of the three, is called the crest of the 



