KNEE JOINT. 261 



and its internal surface is very prominent ; around the margin 

 of this surface, and especially at the under part of it, the adi- 

 Fig. 65.* pose substance found in joints is very^abun- 

 dant. On each side of the adipose mass, 

 under the patella, is a plait of the synovial 

 membrane, called ligamentum alare minus, 

 and majus ; and a process of the mem- 

 brane, called ligamentum mucosum passes 

 from the neighborhood of the adipose 

 mass to the os femoris between the con- 

 dyles. 



These processes retain the adipose sub- 

 stance in its proper place, during the motions 

 of the joint. 



There are two very strong ligaments, called the anterior and 

 posterior crucial, which arise from the middle protuberance of 

 the tibia, one of which is inserted posteriorly into the corner face 

 of the external condyle of the os femoris, and the other, into 

 the outer face of the internal. These ligaments decussate each 

 other partially, on which account the name crucial is applied to 

 them. They are in a state of tension when the leg is extended, 

 and prevent it from moving farther forward : when it is bended 

 they are relaxed. They add greatly to the strength of the 

 connexion between the os femoris and tibia. 



These ligaments are generally supposed to be in the cavity of 

 the joint ; but the synovial membrane is reflected round them in 

 such a manner that they are exterior to it. 



In addition to the crucial ligaments, this articulation has the 

 following external supports. 



When the leg is extended, these ligaments are tense, they* 

 therefore prevent rotation in the extended state: when the 



* Posterior view of the ligaments of the knee joint. 1. Posterior ligament of 

 "Winslow, connected by a tendinous expansion with 2, the tendon of the semi- 

 membranous muscle ; the latter is cut short. 3. The process of the tendon, 

 which spreads out in the fascia of the popliteus muscle. 4. A process which is 

 sent inwards beneath the internal lateral ligament. 5. The posterior part of the 

 internal lateral ligament. 6. The long external lateral ligament. 7. Short ex- 

 ternal lateral ligament. 8. Tendon of popliteus cut short. 9. The posterior 

 superior tibio-fibular ligament. 



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