THE KNEE-JOINT 259 



the external, and has an outline more oval than circular. Its anterior cornu is 

 wide, and has a broad and ol)lique attachment to the anterior margin of the head 

 of the tibia. It reaches backwards and outwards from the margin of the tuberosity 

 towards the middle of the fossa in front of the til)ial spine, being altogether in front 

 of the anterior crucial ligament. The posterior cornu is tirmly fixed by a broad 

 insertion in an antero-posterior line along the inner side of the posterior fossa, from 

 the internal tul^ercle of the spine to the posterior margin of the head of the tibia. 

 Its convex border is connected with the internal lateral ligament and the semimem- 

 brannsus tendon. • 



The transverse ligament (figs. 246 and 247) is a rounded, slender, short cord, 

 which extends from the convex border of the external semilunar cartilage to the 

 concave border or anterior cornu of the internal, near Avhich it is sometimes attached 

 to the bone. It is an accessory band of the external cartilage, and is situated 

 beneath the synovial membrane. 



The coronary ligaments (fig. 246) connect the margins of the semilunar fi))ro- 

 cartilages with the head of the tibia. The external is much more lax than the 

 internal, permitting the outer cartilage to change its position more freely than 

 the inner. They are not in reality separate structures, but consist of fibres of the 

 several surrounding ligaments of the knee-joint which become attached to, as they 

 pass over the margins of the fibro- cartilages. 



The synovial membrane (fig. 249) of the knee forms the largest synovial sac 

 in the bodv. Bulging upwards from the patella, it follows the capsule of the joint 

 into a large rul-de-snc beneath the tendon of the extensor muscles on the front of 

 the femur. It reaches some distance beyond the articular surface of the bone, and 

 communicates very frequently with a large bursa interposed between the tendon 

 and the femur above the line of attachment of the capsular ligament. After invest- 

 ing the circumference of the lower end of the femur, it is reflected upon the fibrous 

 envelope of the joint formed by the capsular, posterior, and lateral ligaments. It 

 covers a great portion of the crucial ligaments, but leaves uncovered the back of the 

 posterior crucial where the latter is connected with the posterior ligament, and the 

 lower part of both crucial ligaments where they are united. Thus the ligaments 

 are completely shut out of the synovial cavity. Along the fibrous envelope the 

 synovial membrane is conducted down to the semilunar cartilages, over both sur- 

 faces of which it passes, and is reflected off the under surface on to the coronary 

 ligaments, and thence down to the head of the tibia, around the circumference of 

 which it extends a short way. It dips down between the external cartilage and the 

 head of the tibia as low as the superior tibio-fibular ligament, reaching inwards 

 nearly as far as the popliteal notch, and forming a bursa for the play of the 

 popliteal tendon. 



At the back of the joint two pouches are prolonged beneath the muscles, one on 

 each side between the condyle of the femur and the origin of the gastrocnemius. 



Large processes of synovial memlirane also project into the joint, and being 

 occupied by fat serve as padding to fill up spaces. The chief of these processes, 

 the ligamentum mucosum (figs. 248 and 249) springs from the infrapatellar fatty 

 mass. This so-called ligament is the central portion of the large process of synovial 

 membrane, of which the alar ligaments form the lateral free margins. It extends 

 from the fatty mass, below the patella, backwards and upwards to the inter- 

 condyloid notch of the femur, where it is attached in front of the anterior crucial, 

 and to the outer side of the posterior crucial ligament. Near the femur it is thin 

 and transparent, consisting of a double fold of SAniovial memljrane, Init near the 

 patella it contains some fatty tissue. Its anterior or upper edge is free, and fully 

 an inch (2-5 cm.) long; the posterior or lower edge is half the length, and is 

 attached to the crucial ligaments above, Init is free below. 



Passing backwards from the capsule on each side of the patella is a prominent 

 crescentic fold formed by reduplications of the synovial membrane — these are the 

 alar ligaments (fig. 248). Their free margins are concave and thin, and are lost 

 b(4(nv in the ligamentum mucosum. There is a slight fossa above and another 

 below eacl) ligament. 



The arterial supply is derived from the anastomotica femoris; the superior and 

 inferior internal and external articular; the azygos articular; the descending 



