448 THE INFERIOR EXTREMITY 



receive no muscular support. Owing to this lack of support 

 and to the action of gravity, these veins are very liable to 

 become varicose. Both veins contain numerous valves, which 

 help to support the column of blood. The rupture of one of 

 these valves increases the strain on the one distal to it, which 

 in turn gives way. The unsupported vessel walls are not strong 

 enough to support the column of blood when the patient is in 

 the erect attitude, and they consequently become dilated and 

 varicose. The middle third of the great saphenous vein is most 

 frequently affected, but its proximal and distal parts and the 

 small saphenous vein are often involved. 



When the patient adopts the recumbent posture, the veins, 

 though varicose, are able to fulfil their function, and in conse- 

 quence, elastic bandages, stockings, etc., which are used as a 

 mechanical support, should be applied before the patient rises 

 from this posture. 



Owing to the obstruction to the venous return the vitality 

 of the skin is diminished, especially in the distal part of the 

 limb, and chronic ulceration tends to arise after trivial injuries 

 in this region. Healing is always tedious and may not occur 

 unless the patient is kept in bed with the limb slightly elevated. 

 This position assists the venous return, and so improves the 

 vitality of the affected part. 



The Bursae around the Knee. Numerous bursse, some 

 of which communicate with the interior of the joint, lie in 

 relation to the tendons around the knee. 



Anterior. (i) The supra-patellar bursa almost invariably 

 communicates with the joint. It lies behind the tendon of 

 the quadriceps and is separated from the femoral diaphysis by 

 an extra-synovial pad of fat (Fig. 131). It extends upwards 

 for a hand-breadth above the proximal border of the patella, 

 and is outlined in hydrops of the joint. Fluid may be aspirated 

 from the knee-joint through this bursa. 



(2) The prepatellar bursa is subcutaneous and lies in front 

 of the distal part of the patella and the proximal part of the 

 ligamentum patellae. When the bursa is exposed to much 

 pressure, effusion is apt to occur into it and the condition may 

 become chronic, with the formation of fibrous bands and " melon- 

 seed " bodies (" housemaid's knee "). The prepatellar bursa, 

 when thus affected, may be removed through a semilunar 

 incision, the base of which is distal, so that pressure on the scar 

 is subsequently avoided. 



