THE REGION OF THE KNEE 



457 



violently rotated laterally, the lateral meniscus is able to follow 

 the movements of the lateral condyle, and in doing so it exerts 

 a strain on the thin concave margin of the medial meniscus 

 through the transverse ligament. As a result a concentric 

 splitting may occur in the anterior part of the medial meniscus, 

 or its anterior extremity may be torn through and dragged 

 towards the centre of the joint (Fig. 134, B). 



In some subjects, either owing to their occupation or as the 



FIG. 134. Diagram to illustrate Injuries of the Medial Meniscus. 



A. Normal position of the menisci. 



B. Splitting of the medial meniscus caused by traction on the transverse ligament, 

 following violent lateral rotation of the femur on the fixed tibia. 



C and D. Tearing of the anterior attachment of the medial meniscus caused by violent 

 flexion of the knee combined with medial rotation of the femur on the fixed tibia. 



result of a constitutional disease, the capsule of the knee-joint 

 becomes sufficiently relaxed to permit a slight amount of 

 abduction and adduction. This constitutes a predisposing 

 cause to injury, as, owing to the increased freedom of separation 

 of the femur and tibia from each other, the menisci are more 

 likely to be caught between the two articular surfaces. In 

 extension of the knee-joint the somewhat flattened distal surface 

 of the medial condyle of the femur is in contact with the whole 

 of the medial meniscus. When the leg is extended, therefore, 

 forcible medial rotation of the femur on the tibia produces little 

 alteration in the shape of the meniscus. On the other hand, 



