THE POPLITEAL FOSSA 631 



The Perforating Arteries (Fig. 544), usually three in number, are so named because 

 they perforate the tendon of the Adductor magnus to reach the back of the thigh. 

 They pass backward close to the linea aspera of the femur under cover of small 

 tendinous arches in the muscle. The first is given off above the Adductor brevis, 

 the second in front of that muscle, and the third immediately below it. 



The first perforating artery (a. perforans prima) passes backward between the Pec- 

 tineus and Adductor brevis (sometimes it perforates the latter); it then pierces 

 the Adductor magnus close to the linea aspera. It gives branches to the Adductores 

 brevis and magnus, Biceps femoris, and Glutseus maximus, and anastomoses with 

 the inferior gluteal, medial and lateral femoral circumflex and second perforating 

 arteries. 



The second perforating artery (a. perforans secunda), larger than the first, pierces 

 the tendons of the Adductores brevis and magnus, and divides into ascending 

 and descending branches, which supply the posterior femoral muscles, anasto- 

 mosing with the first and third perforating. The second artery frequently arises 

 in common with the first. The nutrient artery of the femur is usually given off 

 from the second perforating artery; when two nutrient arteries exist, they usually 

 spring from the first and third perforating vessels. 



The third perforating artery (a. perforans tertia) is given off below the Adductor 

 brevis; it pierces the Adductor magnus, and divides into branches which supply 

 the posterior femoral muscles; anastomosing above with the higher perforating 

 arteries, and below with the terminal branches of the profunda and the muscular 

 branches of the popliteal. The nutrient artery of the femur may arise from this 

 branch. The termination of the profunda artery, already described, is sometimes 

 termed the fourth perforating artery. 



Numerous muscular branches arise from the profunda; some of these end in the 

 Adductores, others pierce the Adductor magnus, give branches to the hamstrings, 

 and anastomose with the medial femoral circumflex artery and with the superior 

 muscular branches of the popliteal. 



The highest genicular artery (a. genu suprema; anastomotica magna artery) (Fig. 

 550) arises from the femoral just before it passes through the opening in the 

 tendon of the Adductor magnus, and immediately divides into a saphenous and a 

 musculo-articular branch. 



The saphenous branch pierces the aponeurotic covering of the adductor canal, 

 and accompanies the saphenous nerve to the medial side of the knee. It passes 

 between the Sartorius and Gracilis, and, piercing the fascia lata, is distributed to 

 the integument of the upper and medial part of the leg, anastomosing with the 

 medial inferior genicular artery. 



The musculo-articular branch descends in the substance of the Vastus medialis, 

 and in front of the tendon of the Adductor magnus, to the medial side of the knee, 

 where it anastomoses with the medial superior genicular artery and anterior recur- 

 rent tibial artery. A branch from this vessel crosses above the patellar surface 

 of the femur, forming an anastomotic arch with the lateral superior genicular 

 artery, and supplying branches to the knee-joint. 



THE POPLITEAL FOSSA (Fig. 551). 



Boundaries. The popliteal fossa or space is a lozenge-shaped space, at the 

 back of the knee-joint. Laterally it is bounded by the Biceps femoris above, 

 and by the Plantaris and the lateral head of the Gastrocnemius below; medially 

 it is limited by the Semitendinous and Semimembranosus above, and by the medial 

 head of the Gastrocnemius below. The floor is formed by the popliteal surface 

 of the femur, the oblique popliteal ligament of the knee-joint, the upper end of the 

 tibia, and the fascia covering the Popliteus; the fossa is covered in by the fascia lata. 



