POPLITEAL ARTERY. 



63 



and inferior thirds, and descends obliquely 

 outwards and from before, backwards through 

 the popliteal space, to the lower border of the 

 popliteus muscle, where it terminates, after 

 having gradually diminished somewhat in size, 

 by dividing into the anterior and posterior 

 tibial arteries. When viewed with regard to 

 the vertical axis of the popliteal region, the 

 artery certainly takes an oblique course out- 

 wards ; but in reference to the mesial and 

 perpendicular line of the body, this obliquity 

 is more apparent than real, and depends upon 

 the direction inwards which the shaft of the 

 thigh bone follows ; and this appears evident 

 by the artery passing vertically and midway 

 between the condyles of the femur. Its course 

 from before backwards is very decided until it 

 has attained the superior border of the popli- 

 teus muscle; but as the lower portion of the 

 popliteus is on a plane a little anterior to the 

 upper, and as the artery is applied upon its 

 posterior surface the course will be changed 

 for a direction forwards, so that the artery 

 describes a slight curve, convex backwards, 

 and the concavity corresponding with the 

 back of the knee-joint. When the leg is 

 flexed upon the thigh, the popliteal artery 

 follows the bend of the articulation, and is 

 curved forwards without lateral tortuosity, 

 the curve agreeing with the angle of flexion ; 

 this alternate straightening and bending of the 

 artery during the movements of the leg has 

 been assigned as a reason for its being so 

 frequently the seat of aneurism ; on the other 

 hand, it has been stated that forced extension 

 of the leg, carried even to rupture of the liga- 

 ments of the joint, may be made without in- 

 jury to the artery. The popliteal artery is 

 closely related to its accompanying vein ; as 

 they are entering the space, the vein lies to 

 the outer side of the artery, and superficial or 

 posterior to it, and changes its relation near 

 the joint only to become still more directly 

 posterior : they are enveloped in a common 

 sheath, which is continued from the femoral 

 region (see FEMORAL ARTERY), and by which 

 they are intimately connected with each other. 

 The artery is at first deeply seated in the 

 popliteal region, and guided into it by the 

 inferior boundary of the elliptical tendinous 

 opening ; it then descends obliquely upon the 

 flat triangular surface of the femur to the 

 knee-joint, resting in its course upon a cushion 

 of fat which is interposed between it and the 

 bone, and thicker below than above, so as to 

 well support the artery as it inclines back- 

 wards from the femur to reach the posterior 

 aspect of the joint. For some distance from 

 its commencement it is concealed beneath the 

 semimembranosus muscle, the thick fleshy belly 

 of which obliquely crosses it behind ; emerging 

 from under cover of this muscle, the artery 

 continues its course to the condyles of the 

 femur, between the biceps on the outer side, 

 and semimembranosus and semitendinosus on 

 the inner ; a considerable quantity of fat sepa- 

 rates it from, posteriorly, the aponeurotic 

 fascia, closing in the space behind, and from 

 the skin. As the internal popliteal or tibial 



nerve descends vertically in the axis of this 

 region, it must necessarily lie to the outer 

 side of the artery in this part of its course ; 

 and as the nerve is found almost immediately 

 beneath the fascia, it is therefore superficial or 

 posterior to the artery, from which it is sepa- 

 rated by more or less fat. While thus buried 

 in fat, three or four lymphatic glands are 

 closely related to the artery, often indeed sur- 

 rounding it, one to either side, another super- 

 ficial, and a fourth occasionally found between 

 it and the femur. Should any of these glands 

 become enlarged, the impulse such swelling 

 would receive from the artery might lead to 

 its being mistaken for aneurism. We next 

 find the popliteal artery crossing the bend of 

 the knee-joint, and resting upon its posterior 

 ligament ; it descends between the condyles 

 of the femur and the two heads of the gas- 

 trocnemius to the upper border of the popli- 

 teus muscle : the little fleshy belly of the 

 plantaris is also related to its outer side. In 

 this stage the accompanying vein is more 

 directly behind it, and the tibial nerve, coming 

 into closer relation with the artery, from 

 which it is separated by the vein, is also pos- 

 terior or superficial to it, with a tendency to 

 cross to its inner side. At this part of its 

 course the nerve usually sends off, first, the 

 communicans tibialis, and then its branches 

 to the heads of the gastrocnemius, so that the 

 relation which the nerve and its branches have 

 to the artery at this point will readily account 

 for the pain or numbness generally attendant 

 on aneurismal tumours in this region ; so, also, 

 for oedematous swelling of the leg under the 

 same circumstances, we have only to refer to 

 the relative anatomy of the vein and artery for 

 its explanation ; posteriorly, the artery is sepa- 

 rated from the fascia and integument by more 

 or less fat, and is still a considerable distance 

 from the surface; for the tendons of the ham- 

 string muscles, and the condyles of the femur 

 with the heads of the gastrocnemius, so bear 

 off from the artery the skin and fascia as to 

 leave it in a deep and narrow hole, resting upon 

 the posterior ligament of the joint, and con- 

 cealed behind by, first, the vein, and then the 

 tibial nerve. Of course any operation upon the 

 artery while thus situated would be impracti- 

 cable. Lastly, the artery gains the posterior 

 surface of the popliteus muscle, upon which 

 it descends to terminate by dividing into the 

 anterior and posterior tibial vessels ; this divi- 

 sion occurs at the lower border of the muscle, 

 and opposite the interval between the tibia and 

 fibula. The artery is deeply concealed between 

 the heads of the gastrocnemius as they ap- 

 proach each other to unite; the tibial nerve 

 crosses to gain its inner side, and the vein, 

 which often receives the tibio-peroneal vein 

 while upon the popliteus, is still posterior to 

 the artery. 



Varieties. The popliteal artery very seldom 

 exhibits any deviation from its usual arrange- 

 ment ; occasionally, its point of division occurs 

 higher in the popliteal space. Professor Har- 

 rison mentions to have seen the artery divide 

 between the condyles of the femur. Instances 



