THE ARTICULAR ARTERIES. 



463 



brancli fi'om the anterior tibial ; whilst others ascend, and anastomose with the 

 upper articular arteries. 



(^0 The middle or azijgos articular artery is a small branch which arises opposite 

 the flexure of the joint, and, piercing the posterior ligament, supplies the crucial 

 ligaments and other structures withm the articulation. 



Fig. 296. — Anterior view of the Deep Akterial Fig. 2GS. 



Branches surrounding the Knee-.Toint and their 

 Anastomoses (from Tiedemanu). \ 



a, the patellar articular surface of the femur ; h, the 

 posterior surface of the patella which, with the ligamentura 

 patellis, has been turned down ; c, the head of the fibula ; 

 ] and 2, branches of the internal superior articular branch 

 of the popliteal ramifying on the periosteum, and anasto- 

 mosing with the external superior articular branch 3, and 

 with other arteries within and below the joint ; 4, branches 

 of the internal inferior articular ; o, external inferior 

 articular ; 6, recurrent of the anterior tibial artery. 



Varieties. — Deviations from the ordinary condition 

 of the popliteal artery are not frequently met with. 

 The principal departure from the ordinary arrange- 

 ment consists in its high di^asion into terminal 

 branches. Such an early di\'ision has been found to 

 take place most frequently opposite the flexure of 

 the knee-joint, and not higher. 



In a few instances, the popliteal arteiy has been 

 seen to divide into the anterior tibial and peroneal 

 arteries — the posterior tibial being small or absent. 

 In a single case, the popliteal artery was found to 

 divide at once into three terminal vessels, viz., the 

 peroneal and the anterior and posterior tibial arteries. 



The azyc/os articular branch frequently arises from one of the other articular 

 branches, especially from the upper and external branch. There are sometimes 

 .several small middle articular branches. 



POSTERIOR TIBIAL ARTERY. 



The posterior tibial artery is situated along the back part of the 

 leg, between the superficial and deep layers of muscles, and is firmly 

 bound down to the deep muscles by the fascia which covers them. It 

 extends from the lower border of the popliteus muscle, where it is 

 continuous with the popliteal artery, down to the inner side of the 

 calcaneum, where it terminates beneath the origin of the abductor 

 poUicis muscle by dividing into the external and internal plantar 

 arteries. 



Placed at its origin opposite the interval between the tibia and 

 fibula, it approaches the inner side of the leg as it descends, and lies 

 behind the tibia ; at its lower end it is placed midway between the 

 inner malleolus and the prominence of the heel. Very deeply seated 

 at the upper part, where it is covered by the fleshy portion of the 

 gastrocnemius and soleus muscles, it becomes comparatively superficial 

 towards the lower part, being there covered only by the integument and 

 two layers of fascia, and by the annular ligament behind the inner 

 malleolus. It lies successively upon the tibialis posticus, the flexor 

 longus digitorum, and, at its lower end, directly on the tibia and the 

 ankle-joint. Behind the ankle, the tendons of the tibialis posticus 

 and flexor longus digitorum lie between the artery and the internal 



