3 i8 INFERIOR EXTREMITY 



condyle, and the corresponding part of the medial condyle, are exhausted. 

 This movement of the femoral condyles has been compared to that of "a 

 wheel partially restrained by a drag " (Goodsir). Any additional movement 

 beyond this point must necessarily take place in connection with the anterior 

 oblique third of the medial condyle. This produces a rotation or screw- 

 like motion of the femur medially. The medial condyle travels backwards 

 round the spine of the tibia, and the anterior part of the intercondylar 

 fossa comes into contact with the anterior crucial ligament and the medial 

 tubercle of the tibial spine (Bruce Young). The joint is now "screwed 

 home" or locked. In the initial stage of flexion the reverse movement 

 must be accomplished. The unlocking of the joint can only be brought 

 about by a rotation medially of the tibia, or a rotation laterally of the 

 femur. 



When fully extended, as we have seen, the joint is locked, and the 

 posterior part of the capsule, the collateral ligaments, and the anterior 

 crucial ligaments are tense. The limb is converted into a rigid column, 

 and the upright posture is thereby maintained with the smallest possible 

 degree of muscular exertion. 



The muscles which operate upon the bones of the leg so as to produce 

 flexion and extension of the limb at the knee-joint are : (i) extensors, the 

 four parts of the quadriceps extensor ; (2) flexors, the biceps femoris, 

 popliteus, sartorius, gracilis, semitendinosus, and semimembranosus. Of 

 these, only one is inserted on the lateral side of the limb, viz. the biceps. 

 The other five are inserted into the tibia on the medial side of the leg. 



Dissection. In order to obtain a proper view of the attachments of the 

 crucial ligaments the following dissection should be made : The femur 

 must be sawn across about two inches proximal to its distal articular surface. 

 When this is done the saw should be applied to the cut surface of the distal 

 part of the bone, and a vertical cut made through it so as to divide it into 

 a right and a left lateral portion. The saw-cut should be planned to end 

 inferiorly in the intercondylar fossa between the condyles and between 

 the proximal attachments of the two crucial ligaments. By this procedure 

 the crucial ligaments can be studied singly, or together, and their relation 

 to the collateral ligaments of the joint can be examined. It will be seen that 

 the fibular collateral ligament and the anterior crucial ligament constitute a 

 pair of ligaments appropriated by the lateral condyle, to either side of 

 which they are fixed ; while the tibial collateral and the posterior crucial 

 ligaments belong to the medial condyle of the femur, and are attached on 

 either side of it. When this relationship is observed, the tibial collateral 

 ligament may be divided. This will, in a measure, set free the medial 

 condyle, and give greater space for the study of the crucial ligaments. 



Ligamenta Cruciata Genu (O.T. Crucial Ligaments). The 



cruciate ligaments are well named, because they cross each 

 other, like the limbs of the letter X, in the interval between 

 the two condyles of the femur. This crucial arrangement 

 is seen whether they are viewed from the side, by the removal 

 of the distal part of one condyle, or from the front or the 

 back of the joint The anterior cruciate ligament is attached 

 to the lateral condyle, whilst the posterior is fixed to the 

 medial condyle of the femur. They are consequently some- 

 times termed lateral and medial. 



