44 SURGICAL APPLIED ANATOMY. [Chap. xxi. 



in connection with the causation of the lesion, that in 

 flexion and extension the two cartilages move with the 

 tibia upon the femur, but in the rotation movements 

 of the leg the discs are fixed, and the tibia rotates 

 beneath them. The luxated cartilage may be displaced 

 either inwards towards the tibial spine, or inwards and 

 backwards, or outwards so as to slip beyond the mar- 

 gins of the two articulating bones. Although statistics 

 are wanting that would show which cartilage is the 

 more often luxated, anatomical facts would point to the 

 outer disc as the one the more likely to be displaced. 

 This disc is much more movable than its colleague. 

 The internal cartilage and its coronary ligament are 

 adherent to both the posterior and internal lateral 

 ligaments by extensive attachments j while the outer 

 cartilage has only a somewhat feeble connection with 

 the ligamentum posticum and the hinder of the crucial 

 bands. 



Geim-valgiim, or knock-knee. In this affection, 

 owing to changes in and about the joint, the tibia 

 and femur are bent laterally, and the angle formed by 

 the outer borders of the thigh and leg becomes more 

 or less conspicuously diminished. The appearances 

 produced by this affection are familiar. When a 

 person stands erect with the feet together, the tibiae 

 are practically vertical, and the femora meet them at a 

 certain angle. The degree of this angle depends, in 

 normal subjects, to a great extent upon the relative 

 wiclfch of the pelvis. The greater this width the less 

 is the angle between the outer sides of the femur and 

 leg. Compared with men, many women, on account 

 of the relatively greater width of their pelves, may be 

 said to be in a sense knock-kneed. In actual genu- 

 valgum, the tibiae cease to be vertical in the erect 

 position ; their lower ends deviate more and more from 

 the middle line, until the distance between the two 

 malleoli becomes considerable when the individual 



