THE KNEE-JOINT 



261 



some slight amount of rotation in the bent position. These movements are not so 

 simple as the corresponding ones at the elbow, for the knee is not a simple hinge 

 joint. The rotation inwards and outwards are movements of the tibia with tlie 

 fibula upon the condyles of the femur. 



The knee differs from a true hinge jdint like the ell)Ow or ankle, in the following 

 particulars : — 



1. The jjoints of contact of the femur with the tibia are constantly changing. 



Fig. 250. — The Lateral Ligaments of the Kxee in Flexion and Extension. 



Tlius, in the flexed position, the hinder part of the articular surface of the tibia is 

 in contact with the rounded back part of the condyles; in the semiflexed position 

 the middle parts of the tibial facets articulate with the anterior rounded part of the 

 condyles; while in the fully extended position the anterior and middle parts of the 

 til)ial facets are in contact with the anterior flattened portion of the condyles. So 

 with the patella: in extreme flexion the inner articular facet rests on the outer part 



