MECHANISM OF THE KNEE-JOINT. 233 



in a plane, oblique at once to the antero-posterior plane of the 

 condyle and to the horizontal plane of the joint, and inter- 

 calated "between the antero-posterior portion of the condyle 

 and the patellar surface. This intercalated portion may, ac- 

 cording to Meyer, be conceived as a segment of the base of a 

 cone, the vertex of which, in the erect position of the limb, is 

 situated in the external condyle of the tibia, with its axis 

 directed from above forwards and inwards, to below, back- 

 wards and outwards. The curve extends over 60, and the 

 axis of the generating cone inclined 45 to the horizontal. 



This axis he distinguishes as the oblique axis of the joint, 

 and round it the leg and thigh are compelled to rotate, at the 

 close of extension and the commencement of flexion, when 

 the conical surface in question is in contact with the lateral 

 internal and anterior part of the inter-condyloid spine of the 

 tibia and the anterior crucial ligament. 



Eeferring to the unsatisfactory character of the series of 

 co-ordinates on which the Webers based their assumption of 

 an equiangular spiral as the profile curvature of the femoral 

 condyles, Meyer concluded from measurements procured from 

 outlines of the curve made by means of a tracing-frame and a 

 telescope, that its posterior and anterior portions may be safely 

 assumed to be arcs of two circles, respectively 120 and 40, 

 .the radius of the former being to that of the latter as 5 to 9. 

 He conceives, therefore, that there are two transverse axes of 

 rotation in the knee-joint, an anterior and a posterior ; but 

 holds that, in treating the subject, one transverse axis only 

 need be assumed. 



Whatever exceptions may be taken to Meyer's double 

 transverse axis, and to his assumed circular profile curve of the 

 femoral condyles, there can be no doubt of the general correct- 

 ness and great value of his observations on the so-called oblique 

 rotation of the joint, the corresponding arrangement of the 

 inner condyle, the coadjusted movements of the patella, and 



