ANATOMY OF THE KNEE-JOINT, 225 



configuration and relation of its articular surface ^vill Ix* 

 detected. Instead of two faces, a greater external, and a 

 lesser internal, separated by a perpendicular ridge, as usually 

 described, the surface presents, in every instance, six, frequently 

 seven, facets, sepamted from one another by two perpendicular 

 and two transverse ridges. The external perpendicular ridge 

 is the one commonly describecL The int<.'rnal cuts off a small 

 elongated perpendicular facet at the inner edge of the surface. 

 The two transvei*se ridges oidy extend inwards to the inner 

 perpendicular ridge, so as to separate from above, downwards, 

 two superior, two middle, and one or two inferior facets, the 

 external of the two latter being constant. The relations of the 

 articular surface of the patella present four groups. In 

 complete flexion, the internal or perpendicular facet i.-^ in 

 contact witli a remarkable crescentic facet, which bounds the 

 oblique curvature of the inner condyle of the femur. In none 

 of the other positions of the joint is this internal patellar facet 

 in contact with an opposite cartdaginous surface, but is 

 covered or sheathed by what may be denominated the internal 

 patellar pad. At the same time, the external superior facet 

 lies upon the fore part of the external condyle of the femur 

 below and behind its bounding groove. These two facets are 

 the only parts of the patella which come in contact with the 

 proper femoral condyles. They do so only in complete flexion ; 

 and in this state all the remaining facets are in contact with 

 the great infra-patellar pad, and the so-called mucous liga- 

 ment. 



In the second stage of extension, the superior internal and 

 external facets are in contact with the inierior ix)rtions, 

 respectively of the inner and outer halves of the femoral 

 trochlea ; the internal perpendicular facet being sheathed as 

 before stated ; and the remaining facets being in contact with 

 the great infra-patellar paiL 



In the third stage of extension, the superior internal and 



