The Lower Extremity and Pelvis 



153 



the' femur ; when the knee is bent the patella is carried downwards and backwards 

 on to the under aspect of the femur, where the trochlear surface is prolonged on to the 

 inner condyle. Articulate the two bones and slide the patella down until it lies in the 

 position it would assume in flexion, and it is evident that the bone becomes somewhat 

 tilted up on the~outer condyle, with the result that it is only the inner part of its 

 articular surface which rests against the inner condyle ; at the same time the shape of 



femur 



FIG. 127. Vertical antero-posterior section through knee-joint. 



the trochlear surface is such that the outer part of the patella is not in contact with the 

 outer condyle, but the tilting is really due to the direction and level of the concavity 

 in which the median ridge of the patella rides. 



A rough sloping area extends between the lower margin of the articular surface and 

 the point of the apex, and can be subdivided by the line a (Fig. 126) into two parts, an 

 upper b and a lower c. The lower area c extends to the apex and is for the attachment 

 of the patellar tendon, while the infrapatellar pad of fat, that lies deep to the tendon, 



