THE REGION OF THE KNEE 447 



pus lies from the surface, its presence is difficult to determine 

 at an early stage, but early diagnosis is necessary, as when 

 evacuation is delayed the abscess cavity takes a long time to 

 granulate up. This slow closure is partly due to the rigid walls 

 of the cavity, which are formed by the hamstring tendons, and 

 partly to the destruction of the fat in which the lymph glands 

 are embedded. 



Abscesses in the popliteal fossa are best approached from 

 the lateral aspect of the knee. An incision is made behind the 

 lateral intermuscular septum (p. 402), but in front of the biceps 

 tendon. When the deep fascia is divided, a pair of dressing 

 forceps can be passed medially between the biceps and the 

 femur, and the pus is evacuated by Hilton's method in order to 

 avoid injuring the large vessels and nerves. 



The Popliteus Muscle arises within the capsule of the knee-joint from 

 the lateral aspect of the lateral femoral condyle. It passes distally and 

 medially across the joint, and is inserted into the proximal part of the posterior 

 surface of the tibia. Near its origin the popliteus intervenes between the 

 lateral meniscus (semilunar cartilage) and the fibular collateral ligament (p. 

 455). It is supplied by the tibial (int. popliteal) nerve (L. 4, 5, and S. i) 

 and acts as a flexor of the knee-joint. In addition, when the tibia is fixed 

 the popliteus acts as a lateral rotator of the femur, and when the tibia is free 

 to move it acts as a medial rotator of the tibia. 



Superficial Veins of the Lower Limb. A venous arch 

 extends across the dorsum of the foot near the heads of the 

 metatarsal bones. It is continued backwards along the medial 

 border of the foot as the great saphenous vein, which ascends in 

 front of the medial malleolus and then along the medial border 

 of the tibia to the medial side of the knee-joint. The remainder 

 of its course may be indicated by a line joining the adductor 

 tubercle to the fossa ovalis (p. 401). At the latter point the 

 great saphenous vein passes through the deep fascia and joins 

 the femoral vein. 



The small saphenous vein arises at the lateral extremity of 

 the dorsal venous arch and passes backwards along the lateral 

 border of the foot. From behind the lateral malleolus it 

 ascends obliquely in the superficial fascia of the back of the 

 leg, and near the centre of the popliteal fossa it pierces the 

 fascial roof to join the popliteal vein. It usually communicates 

 with the great saphenous by a branch which winds round the 

 postero-medial aspect of the knee, or by one which arises at a 

 lower level and crosses in front of the proximal part of the tibia. 



Except for a short distance from their termination, both 

 saphenous veins lie in the superficial fascia and 1 therefore 



