THE STIFLE JOINT 99 



of the external condyle of the femur — i.e., the surface of this condyle 

 which bounds the intercondyloid groove. Its fibres run downwards and 

 forwards and are inserted inferiorly into the outer and roughened aspect 

 of the spine of the tibia. 



The Posterior Crucial Ligament is attached to the anterior portion of 

 the surface of the internal condyle which bounds the intercondyloid 

 groove. Its fibres run downwards and backwards and cross those of 

 the anterior crucial ligament. They also cross the postero-external aspect 

 of the internal semilunar disc and become inserted into a special tubercle 

 which is placed at the back of the internal tuberosity of the tibia 

 immediately below its articular surface. 



The crucial ligaments separate the two joints, which are formed by 

 the condyles of the femur and the tibial tuberosities. 



The External Lateral Ligament. — This is a strong, fibrous band which 

 arises from the higher of the two pits on the outer surface of the 

 external femoral condyle. The lower pit gives origin to the popliteus 

 muscle the tendon of which is concealed by the ligament. The liga- 

 ment passes over the outer surface of the condyle and the external 

 semilunar disc, to be inserted into the outer aspect of the head of the 

 fibula. 



The Internal Lateral Ligament is longer than the external, but is 

 not so powerful. Superiorly it is attached to a tubercle on the excentric 

 surface of the inner condyle of the femur. It descends vertically over 

 the edge of the articular surface of the internal tuberosity of the tibia, 

 where there is placed a small facet covered with articular cartilage. Its 

 play over the facet is facilitated by a little cul-de-sac of the synovial 

 membrane of the internal femoro-tibial joint. The ligament is inserted 

 inferiorly into the roughened area on the internal tuberosity of the 

 tibia. 



The Posterior Common Ligament. — This is in the form of a mem- 

 branous sheet. It is made up of two layers, which are separated 

 superiorly, but blend with each other inferiorly. The superficial 



