THE POPLITEAL AETERY. 



495 



4. The inferior external articular artery takes its course outwards, at first 

 under cover of the outer head of the gastrocnemius and over the tendon of the pop- 

 liteus, afterwards beneath the external lateral ligament of the knee and the tendon 

 of the biceps muscle, and resting against the margin of the external semilunar fibro- 

 cartilage. Having reached the fore part of the joint, it divides near the patella into 

 branches, some of which communicate with the lower internal articular artery and 

 with the recurrent branch from the anterior tibial, while others anastomose with the 

 upper articular arteries. 



5. The middle or azygos articular artery is a small branch~wlrrch arises 

 opposite the flexure of the joint, and pierces the posterior ligament to be distributed 

 to the crucial ligaments and other structures within the articulation. Small twigs 

 also pass forwards in the mucous ligament to the fat at the front of the joint, and 

 communicate with the other articular arteries. 



The upper and lower articular arteries of the popliteal, the anastomotic branch 

 of the femoral, and the anterior tibial recurrent artery form, by their communica- 



Fig. 392. THE DEEP ANASTOMOSES OF THE FRONT OF THE KNEE. 

 (Tiedemann.) J 



or, patellar surface of femur ; 5, posterior surface of the patella which, 

 with the ligamentum patellae, has been turned down ; c, head of fibula ; 

 1 and 2, branches of the anastomotic and superior internal articular 

 arteries, ramifying on the bone and anastomosing with the superior external 

 articular branch 3, and with other arteries within and below the joint ; 

 4, branches of the internal inferior articular ; 5, external inferior arti- 

 cular ; 6, anterior tibial recurrent artery. 



tions over the front of the knee, a superficial wide-meshed 

 network of fine vessels between the fascia and skin, and a 

 deeper and closer network of larger vessels, in contact with 

 the bones, from which numerous offsets proceed to the interior 

 of the joint. 



Varieties, Deviations from the ordinary condition of the 

 popliteal artery are not frequent. The principal departure from 

 the ordinary arrangement consists in the high division of the 

 vessel into its terminal branches. Such an early division has been 

 found to take place opposite the knee-joint, or in the intercondylar 

 fossa of the femur, but not higher. In one case, the artery was 

 continued down to the middle of the leg before dividing (Portal). 



Occasionally the popliteal artery divides into three terminal branches, viz., the anterior 

 and posterior tibial and the peroneal arteries ; or more rarely into anterior tibial and peroneal 

 arteries, the posterior tibial being small or absent. 



The popliteal artery has been seen dividing in the upper part of the popliteal space into 

 two branches which reunited after a separate course of about two inches (A. Ward Collins, 

 Journ. Anat., xx, 32) ; and in another instance a " vas aberrans " passed from the upper end 

 of the popliteal artery to the beginning of the posterior tibial (J. Y. Mackay, " Memoirs and 

 Memoranda in Anatomy," 1889, 176). 



One instance is recorded in which the popliteal artery passed downwards internal to the 

 origin of the inner head of the gastrocnemius muscle, and then turned outwards between that 

 and the internal condyle of the femur, to gain the popliteal space (T. P. A. Stuart). In two 

 or three cases the positions of the artery and vein have been found reversed. The artery is 

 occasionally separated from the vein by an accessory slip of origin of the gastrocnemius 

 muscle (p. 263). 



The azygos articular branch often arises from one of the other articular arteries, especially 

 the superior external branch. There are sometimes several small middle articular branches. 

 Two examples of a small taphenoug artery, formed by the enlargement of the median super- 

 ficial sural branch, and descending with the short saphenous nerve and vein to the back of 

 the external malleolus, have been met with. 



