410 THE INFERIOR EXTREMITY 



under cover of the medial head of the gastrocnemius com- 

 municates with the cavity of the joint, and that through which 

 the tendon of the popliteus emerges, there are several small 

 apertures in the posterior part of the capsule for the trans- 

 mission of vessels and nerves into the interior of the joint. 



Dissection. Make a transverse incision through the quadri- 

 ceps extensor, immediately proximal to the patella, and prolong 

 each end of the incision downwards, about 37 mm. posterior to 

 the patella, to the condyles of the tibia, then turn the patella 

 downwards. The joint is now opened from the front and the 

 following structures can be seen and examined, viz., the synovial 

 lining, the cruciate ligaments, which connect the femur with the 

 tibia, and the menisci, which lie upon and are attached to the 

 tibia. Immediately above the joint, between the distal part of 

 the quadriceps extensor and the front of the femur there is a 

 large suprapatellar bursa which is frequently continuous with the 

 joint cavity. To display the extent of that bursa, split the lower 

 part of the quadriceps by a vertical incision in the middle line 

 of the thigh and turn the two parts aside. 



Interior of the Joint. First note the great pad of soft fat 

 which is placed on the deep surface of the ligamentum patellae. 

 In vertical section the fatty mass is triangular in form (Fig. 181). 

 It is termed the infra-patellar pad, and it fills up the interval 

 between the patella, femur, and tibia, and adapts itself to 

 the varied forms which that recess assumes in the different 

 movements of the joint. It is separated from the interior 

 of the joint by a covering of the synovial layer, and from 

 its surface a fold of that layer extends backwards and 

 upwards to the anterior margin of the intercondylar fossa 

 of the femur, where it is attached. That band is termed 

 the patellar synovial fold (O.T. ligamentum mucosuni). As 

 it approaches the femur it becomes narrow and slender; 

 but where it covers the surface of the infra-patellar pad it is 

 broad and triangular, and presents two free margins which 

 extend along the borders of the distal part of the patella, 

 and receive the name of plicce alares (O.T. ligamenta alaria], 

 It must be clearly understood that these are not ligaments 

 in the ordinary sense of the word, but merely folds of the 

 synovial layer. 



Stratum Synoviale (O.T. Synovial Membrane). As the 

 knee joint is the largest joint in the body its synovial stratum is 

 more extensive than that of any other joint. It lines the deep 

 surfaces of the ligamentous structures of the lateral, medial 

 and anterior parts of the joint. It lines the deep surfaces 



