290 



THE ARTICULATIONS 



The coronary ligaments (fig. 319) connect the margins of the semilunar 

 discs wdth the head of the tibia. The lateral is much more lax than the medial, 

 permitting the lateral disc to change its position more freely than the medial. 

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

 surrounding ligaments of the knee-joint which become attached to the margins 

 of the discs as they pass over them. 



The synovial membrane (fig. 324) of the knee forms the largest synovial sac 

 in the body. Bulging upward from the patella, it follows the capsule of the joint 

 into a large cul-de-sac 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 articular capsule. After 

 investing the circumference- of the lower end of the femur, it is reflected upon the 



Fig. 321. — The Upper Extremity of the Tibia (Anterior View), to show the Rela- 

 tion OF the Articular Capsule of the Knee-joint (in red) to the Epiphysial Line. 



fibrous envelope of the joint formed by the capsular, posterior, and collateral 

 ligaments. 



The synovial membrane covers a pyeat 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 jjart of both crucial ligaments where they are united. Thus the ligaments are com- 

 pletely shut out of the synovial cavity. Along the fibrous envelope the synovial membrane is 

 conductcfi down to the semilunar menisci, over both surfaces 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 

 meniscus and the head of the tibia as low as the superior tibio-fibular ligament, reaching inward 

 nearly as far as the intercondyloid 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 conriyle of the femur and the origin of the gastrocnemius. Large processes of syno- 

 vial membrane also j)roj(;ct into tlie joint, and being occui)iefi by f.'it serve as padding to fill up 

 spaces. The chief of these processes, tlie patellar synovial fold (liganientum mucosum) (figs. 

 322 and 324), springs from the infrapatellar fatty mass. This so-called ligament is the central 



fortion of the large j)rocess of synovial membrane, of which the alar folds form the free margins, 

 t extends from the fatty mass, below the patella, backward and upward to the intercondyloid 

 notch of the femur, where it is attached in front of the anterior crucial, and lateral to the poste- 

 rior crucial ligament. Near tlu^ femur it is thin and transparent, consisting of a double fold of 

 synovial memlirane, but near the i)atella it contains some fatty tissue. Its anterior or upper 

 edge is free, and fully 2.5 cm. (an inch) long; the j)osterior or lower edge is half the length, and 

 is ;ilt!ifhed to the crucial ligaments above, but is free below. 



