ARTICULATIONS 313 



broader in the middle than at either extremity, which springs 

 from the medial condyle of the femur distal to the adductor 

 tubercle. As it descends it inclines slightly forwards, and 

 finally it gains attachment to the margin of the medial 

 condyle and to the proximal part of the body of the tibia 

 below the medial condyle. The main part of the tendon 

 of the semimembranosus extends anteriorly under cover 

 of its posterior border to gain an insertion into the medial 

 condyle of the tibia, whilst more distally the inferior medial 

 genicular vessels are carried forwards between it and the 

 bone. The tendons of the sartorius, gracilis, and semi- 

 tendinosus, lie upon its superficial surface, but are separated 

 from it by an intervening bursa. 



The Posterior Part of the Capsule and the Ligamentum 

 PopliteumObliquum(O.T. Posterior Ligament). The posterior 

 part of the capsule extends as a continuous sheet across the 

 posterior aspect of the joint ; laterally it is continuous with 

 the lateral part of the capsule, which lies medial to the fibular 

 collateral ligament, and medially it fuses with the lateral 

 surface of the tibial collateral ligament as the latter crosses 

 the line of the joint. The lateral head of the gastrocnemius 

 fuses with the proximal part of its lateral portion, and the 

 tendon of the popliteus passes through the distal part of the 

 same portion. The medial part of the posterior portion of the 

 capsule is separated from the medial head of the gastrocnemius 

 by a bursa which communicates medially with the bursa 

 which intervenes between the medial head of the gastro- 

 cnemius and the semimembranosus, and it may communicate 

 anteriorly with the cavity of the joint, through an aperture in 

 the capsule. The intermediate part of the posterior portion 

 of the capsule forms part of the anterior boundary of the 

 fossa poplitea, and is strengthened by a strong oblique band, 

 the oblique popliteal ligament^ which passes proximo-laterally 

 from the distal part of the tendon of the semimembranosus 

 to the medial border of the lateral condyle of the femur. 



In addition to the apertures through which the bursa 

 anterior to 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 into the interior of the joint. 



Dissection. A vertical incision should be made into the joint on either 



