POPLITEAL REGION. 



61 



lower " extremity which occupies the bend 

 of the knee, and includes also the poste- 

 rior surface of the thigh, as high as the 

 junction of its middle and lower thirds, and 

 the back part of the upper fourth of the leg : 

 by its muscular boundaries this region is 

 distinctly defined, and is of a diamond shape, 

 but it is by no means so accurately limited 

 when examined with reference to its surface. 

 The external form of the popliteal region 

 differs materially in the flexed and extended 

 position of the leg ; in the latter case, it has 

 somewhat of an oval outline, the longest dia- 

 meter, which is in the vertical direction, 

 greatly exceeding the transverse : the greatest 

 transverse breadth is at the bend of the knee- 

 joint. The surface presents an elongated 

 rounded projection, which is received above 

 between two narrow ridges diverging from 

 each other as they are traced downwards ; 

 these latter are produced by the stretching of 

 the skin over the tendons of the hamstring 

 muscles, and are rendered still more distinct 

 by a more or less deep groove, which sepa- 

 rates them on either side from the general 

 convexity of the region ; inferiorly, the con- 

 vexity of the surface passes off insensibly to 

 the calf of the leg : these characters are more 

 marked in the strong and muscular. When 

 the leg is bent upon the thigh, the roundness 

 of the upper part of the region is lost, and 

 gives place to more or less of a depression or 

 pit between the still projecting ridges produced 

 by the hamstring muscles ; this depression is 

 popularly known as the hollow of the ham. 



The popliteal region is scooped out into a 

 deep, narrow, diamond-shaped cavity, to which 

 in the following description the term " popli- 

 teal space " will be applied ; it is situated 

 between the diverging hamstring muscles and 

 the converging heads of the gastrocnemius, 

 and is broader above the knee-joint than be- 

 low ; it is filled up by a considerable quantity 

 of fat with areolar tissue, and traversed by 

 the popliteal vessels and nerves ; the semi- 

 tendinosus and semimembranosus muscles on 

 the inner side, and the biceps flexor cruris on 

 the outer, bound this space laterally and 

 above ; the two heads of the gastrocnemius 

 with the plantaris muscle form its lateral 

 boundaries below ; anteriorly it is bounded 

 by the posterior surface of the femur, the 

 knee-joint or rather its posterior ligament, 

 and the popliteus muscle, and is closed in 

 posteriorly or superficially by a strong fascia 

 and the skin : it may be as well to mention, 

 that in dissecting the popliteal space we are 

 looking at it from behind, so that the term 

 superficial relates to its posterior aspect. 

 Before describing the contents of the space, 

 it will be necessary to consider more at length 

 the structures which constitute its boundaries. 



The skin and subcutaneous areolar tissue 

 present no very remarkable features for exami- 

 nation ; the former is marked at the bend of 

 the joint by a few transverse furrows, which 

 are obliterated when the leg is fully extended ; 

 it is smooth and adherent to the subjacent 

 tissue. This latter differs in no respect from 



the same structure elsewhere; it contains a 

 variable amount of fat, and is traversed above 

 by a few filaments from the posterior cuta- 

 neous nerve of the thigh, and below, though 

 not invariably, by the posterior saphena 

 vein. This superficial vessel begins, by small 

 branches, at the outer side of the foot, passes 

 behind the outer malleolus, and crosses ob- 

 liquely to the middle line of the leg, then 

 ascends vertically upon the aponeurosis, which 

 it frequently perforates before reaching the 

 popliteal region, passes into the space between 

 the heads of the gastrocnemius to terminate 

 in the popliteal vein ; it occasionally sends 

 upwards a branch upon the fascia lata, which, 

 winding round the inner side of the thigh, 

 joins the saphena major vein. The commu- 

 nicans tibialis nerve courses with this vein, 

 which it closely accompanies at the lower 

 part of the leg, but is separated from it in the 

 popliteal region by being buried between the 

 heads of the gastrocnemius. The posterior 

 saphena vein is liable to become varicose, but 

 less frequently so than the saphena major : 

 this circumstance is of course readily accounted 

 for by the difference of length and size be- 

 tween the two. 



The fascia lata, descending from the pos- 

 terior surface of the thigh, forms the strong 

 aponeurosis which closes in the popliteal space 

 behind ; stretched across this region, it is 

 connected on either side with the condyles of 

 the femur and the tendons of the extensor 

 muscles of the leg, and continued around the 

 joint ; it is especially fixed to the outer lip of 

 the linea aspera by a septal process of the 

 fascia lata which dips between the vastus ex- 

 ternus and biceps muscles, and on the inner 

 side receives fibres from the tendons of the 

 muscles which pass behind the inner condyle ; 

 it approximates the lateral boundaries of the 

 space, gives to it a greater depth, and protects 

 the vessels and nerves by bearing off from them 

 any undue pressure. By its unyielding and 

 dense structure, aneurismal or other swellings 

 are delayed in their approach to the surface, 

 and for the same reason abscesses are prone to 

 burrow and require an early and free opening. 

 This aponeurosis presents numerous trans- 

 verse fibres, is perforated sometimes by the 

 saphena minor vein, and is adherent by fibrous 

 slips with the subcutaneous areolar tissue ; it 

 is continuous below with the aponeurosis of 

 the leg.' 



The muscles forming the boundaries of the 

 popliteal space will be considered only so far as 

 they relate to it ; their more detailed descrip- 

 tion will be found in the articles MUSCLES OF 

 THE LEG AND THIGH. The semitendinosus 

 muscle, after separating from the biceps, termi- 

 nates in a long, slender tendon, which descends 

 inwards, lying upon the surface of the semi- 

 membranosus ; then crosses the inner head of 

 the gastrocnemius, and placed between it and 

 the tendon of the semimembranosus, winds 

 round the inner condyle to pass to its insertion. 

 The semimembranosus in descending at first 

 crosses obliquely the popliteal artery, continues 

 membranous and fleshy to the condyle of the 



