4o6 



HUMAN ANATOMY. 



from it by the masses of fat just described. It surrounds the lower halves of the 

 crucial ligaments with the fat in a common envelope, so that there is in nature no 

 interval between them. There is but a small chink between the upper halves, 

 though each has its separate sheath. The back of the posterior crucial is partly un- 

 covered by synovial membrane. Synovial fringes formed by the membrane and 

 more or less underlying tissue project from the folds of the alar ligaments, from the 

 ligamentum mucosum, and from near the borders of the patella. 



Bursae. — (i) The most important is a large one under the extensor tendons, 

 just above the capsule, with which it usually communicates. It probably in most 

 cases develops independently of the capsule, which then lies in front of its lowest 



Fig. 421. 



Posterior surface of femur 



Gastrocnemius-, 



Back of capsule 



Internal condyle 



Post, crucial ligament 



Int. semilunar cartilage 

 Tibia 



Gastrocnemius 



• Insertion of anterior 

 crucial ligament 



.External condyle 



Ext. semilunar cartilage 

 Tendon of popliteus 

 Tendon of biceps 



Fibula 



Frontal frozen section of right knee-joint passing through condyles and behind shaft of femur. Seen from behind. 



The superior tibio-fibular joint is opened. 



part, a communication forming subsequently. Such a communication almost 

 always exists in the adult, less frequently in the infant. The opening may be small 

 and well defined or so large that the cavities of the joint and bursa give no sign of 

 subdivision. This carries the cavity of the joint any part of three finger-breadths 

 above the knee-pan. It is possible that sometimes there is a communication from 

 the beginning. (2) Prepatellar bursts are found on the front of the patella 

 at different depths. Directly below the skin is the superficial fascia, often lamel- 

 lated and adherent to the layer beneath it. According to Bize,^ (a) a bursa is 

 present in this superficial layer, usually over the lower half of the patella, in eighty- 

 eight per cent, of knees examined. The next layer is an aponeurotic one continu- 

 ous with the fascia lata, beneath which {b) a bursa is found in ninety-five per cent., 

 most commonly at the inner inferior part. A still deeper {c) bursa occurs beneath 



* Journal de I'Anat. et de la Phys., 1896. 



