IXTEKNAL LIGAMENTS OF THE KXEE. 



The rrtirial liijiirnentx (fig. 83) are two strong fibrous cords 

 between the ends of the tibia and femur, which maintain the bones 

 in contact. They cross one another like the legs of the letter X, 

 and have received their name from that circumstance. One is 

 much anterior to the other at the tibial attachment. 



The anterior ligament (/) is very oblique in its direction, and is 

 longer than the posterior. Iiiferiorly it is attached in front of the 

 spine of the tibia, close to the inner articular surface, reaching back 

 to the inner point of the spine ; 

 superiorly it is inserted into an 

 impression on the hinder part of 

 the inner surface of the external 

 t-Miidyle of the femur. 



The posterior h'ytiment (e), the 

 thicker of the two, is almost 

 vertical between the bones at the 

 back of the joint. By the lower 

 end it is fixed to the hindmost 

 impression of the hollow behind 

 the spine of the tibia, near the 

 margin of the bone ; and above, 

 it i> inserted into an impression 

 at the lower part of the outer 

 surface of the internal condyle, 

 and extending forwards to the 

 centre of the intercondylar fossa. 



Tin- use of these ligaments in 

 the movements of the joint may 

 now be studied after the external 

 ligaments have been cut through. 



As long as both ligaments are 

 whole, the bones cannot be sepa- 

 rated from each other. 



Rotation inwards of the tibia 

 is limited by the anterior crucial. 

 Rotation out is not checked by 

 either ligament ; for the bands un- 

 cross in the execution of the move- 

 ment, and will permit the tibia 

 to be turned hind part foremost. 



Supposing the tibia to move as in straightening the limb, the 

 anterior prevents that bone being carried too far forwards by the 

 extensor muscle, or by external force; and the ligament is brought 

 into action at the end of extension, because the tibia is being put 

 in front of the femur. Its use is shown by cutting it across, and 

 leaving the posterior entire, as then the tibial articulating surfaces 

 can be placed in front of the femoral in the half-bent state of the 

 joint. 



The posterior crucial prevents displacement backwards of the 

 tibia by the flexors or by force: and it is stretched in extreme 



Tw o crucial 

 ligaments. 



Anterior is 

 oblique ; 



its attach- 

 ments. 



FIG. 83. INTKKARTICULAR LIGA- 



MKSTS OF THE KNEE-JOINT. 



. Internal, and b, external 

 semilunar fibro-cartilage ; the latter 

 rather displaced by the bending of 

 the joint. 



c. Posterior crucial ligament, 

 with d, the ascending ligamentous 

 band of the external fibro-cartilage. 



/. Anterior crucial ligament. 



(j. Patellar surface of the femur. 



Their use. 



Both unite 

 the bones. 



Rotation 

 inwards 

 checked by 

 anterior. 



Special use 

 of anterior, 



and poste- 

 rior crucial. 



