Joints of the Lower Extremity. 211 



Articulatio genu (continued) (see also Figs. 260 and 261). The capsula 

 articularis extends over the posterior surface of the common tendon of the m. quadriceps 

 femoris in front close above the patella and goes over at the border of the patella upon 

 the latter so that the whole fades articularis patellae looks into the joint cavity. Thence 

 the capsule runs as a loose membrane separated by abundant fatty tissue from the 

 ligamentum patellae and from the adjoining parts of the retinacula patellae to the upper 

 margins of the two menisci and to the inferior attachment of the ligamentum cruciatum 

 anterius. It then encloses the two ligamenta cruciata genu in a common sheath and 

 goes over at the posterior margin of the ligamentum cruciatum posterius into the posterior 

 wall; thus the two ligamenta cruciata genu form with the surrounding synovial membrane 

 a sort of wall of separation which is shoved in from behind into the joint cavity, dividing 

 this, behind, into a medial and a lateral compartment. From the medial and lateral 

 margin of the facies articularis patellae project two prominent, fatty, synovial folds, plicae 

 alares (0. T. ligamenta alafia) which converge below; they are often studded with 

 synovial villi. At the angle of union of the same there arises a very variable, simple, 

 larger, often fatty, fold, the plica synovialis patellaris (0. T. ligamentum mucosum), 

 which extends backward, in a sagittal direction, free through the joint cavity to become 

 attached at the lowermost margin of the fossa intercondyloidea femoris ; it is the anterior 

 margin of a large sagittal fold of the synovial membrane, originally present, ensheathing 

 the ligamenta cruciata; this fold extends from the posterior capsular wall, without inter- 

 ruption, as far as the patella and divides the joint-cavity from behind into two chambers, 

 corresponding to the two pairs of joint-tuberosities, communicating in front of the fold. 

 This original condition may be preserved wholly or in part. 



The joint cavity is continued upward in the majority of cases directly into the 

 bursa [mucosa] suprapatellaris. This large bursa lies between the anterior surface 

 of the lower end of the femur which has only a slight covering of fat and the posterior 

 surface of the common tendon of the m. quadriceps femoris (see Figs. 260 and 261); 

 it is intimately fused with the latter and separated from the joint cavity, usually only 

 incompletely and indistinctly, by a projecting fold (see Fig. 261). In rarer cases the 

 bursa is completely shut off so that no connection exists between the two cavities, and 

 it then becomes displaced for a variable distance from above downward in front of the 

 capsule of the joint. 



14 



