232 MECHANISM OF THE KNEE-JOINT. 



extension, backwards in flexion, on the nearly horizontal 

 surface of the tibia. 



3. By a peculiar arrangement, certain ligaments become 

 tightened when the knee is extended, and the column or shaft 

 of the limb becomes rigid, and thus fitted more particularly 

 for the mechanical support of the body in its erect position. 



4. The arrangement by which these ligaments become 

 alternately tightened and slackened, is the antero-posterior 

 spiral curvature of the femoral condyles ; the ligaments in 

 question being attached above to the neighbourhood of the 

 polar extremities of the curves, are consequently drawn up 

 and put on the stretch in extension, let down and slackened 

 in flexion. 



5. The ligaments relaxed in flexion permit a rotation of 

 36 in the horizontal plane of the joint, during which the inner 

 condyle of the femur is comparatively fixed, while the outer 

 describes a curve, like the front-wheels of a carriage in pass- 

 ing round a corner. These observations of the Webers on the 

 knee-joint were published in 1836, but have in no respect 

 modified the current modes of viewing and describing this 

 important articulation. 



H. Meyer published, in Miiller's Archivs for 1853, in the 

 course of a series of memoirs on the mechanics of the human 

 skeleton, his observations on the knee-joint. The most im- 

 portant features of this memoir are the observations on the 

 curvatures of the femoral condyles and on the axis of the 

 articulation. Viewing the patellar as distinct from the two 

 condyloid portions of the joint, he pointed out for the first 

 time a feature of the internal condyle of the femur which had 

 previously escaped notice in its proper form. The two pos- 

 terior thirds of this condyle are on the whole parallel to, and 

 of the same length as, the entire external condyle. The pre- 

 viously-recognised greater length, and so-called obliquity, of 

 the inner condyle, depends on the addition of a portion curved 



