590 THE ARTERIES 



vastus internus, wliore it anastomoses (fig. 376) with the deep branch of tlie anas- 

 tomotica magna and termination of tlie profunda alcove, with the inferior internal 

 articular below, and with the superior external articular across the front of the 

 femur. It supjilies small branches to the contiguous muscles, to the femur, to the 

 patella, and to the joint. 



(c) The inferior internal articular, the larger of the two inferior articular 

 arteries, passes o])liquely downwards and inwards across the popliteus, below the 

 internal tuberosity of the tibia, and beneath the internal lateral ligament to the 

 front and inner side of the knee-joint, where it anastomoses (fig. 376), above with 

 the superior internal articular and the superficial l)ranch of the anastomotica magna, 

 and across the front of the tibia with the inferior external articular. It supplies 

 branches to the loAver and inner part of the joint. 



(d) The inferior external articular (fig. 376) passes outwards above the head 

 of the fibula, along the tendon of the })0})liteus muscle, beneath the external head 

 of the gastrocnemius, and then under the tendon of the biceps, and between the 

 long and short external lateral ligaments. Then winding to the front of the joint, 

 it anastomoses above with the superior external articular, below with the anterior 

 tibial recurrent, and across the front of the tibia with the internal inferior articular. 

 It also supplies branches to the outer and lower part of the joint. 



(e) The azygos articular arises from the deep surface of the popliteal artery, 

 and passes, with the articular branch of the obturator nerve, through the posterior 

 ligament, directly into the knee-joint, where it supplies the crucial ligaments, and 

 the ligamenta mucosa and alaria. It anastomoses Avith the intrinsic branches of 

 the other articular arteries. 



(4) The terminal branches of the popliteal are the posterior and anterior tibial 

 arteries. The former appears to be a direct continuation of the vessel, and passes 

 down the back of the leg to the inner ankle, where, on entering the sole of the foot, 

 it divides into the internal and external plantar. The anterior tibial turns forwards, 

 and, passing through the interosseous membrane, descends along the front of the 

 leg, and ends, under the name of the dorsal artery of the foot, l:)y anastomosing, 

 through the first interosseous space, with the external plantar artery in the sole. 



THE POSTERIOR TIBIAL ARTERY 



The posterior tibial artery (fig. 377), the larger of the two branches into which 

 the popliteal divides at the lower border of the popliteus muscle, runs dow'nwards 

 on the flexor aspect of the leg between the superficial and deep muscles to the back 

 of the inner ankle, where, midway between the tip of the internal malleolus and 

 OS calcis, and under cover of the origin of the abductor hallucis as it arises from 

 the internal annular ligament, it divides into the internal and external plantar 

 arteries. 



The artery is first situated midway between the tibia and fibula, and is deeply 

 placed ])encath the muscles of the calf. As it passes downwards it inclines inwards, 

 and at the lower third of the leg is superficial, being only covered by the skin and 

 fascias. At the ankle it lies beneath the internal annular ligament, and at its bifur- 

 cation also beneath the abductor hallucis. A line drawn from the centre of the 

 popliteal space to a spot midway between the internal malleolus and point of the heel 

 will indicate its course. 



Relations. — Anteriorly, from above downwards, it lies successively on the 

 tibialis posticus, the flexor longus digitorum, tlie posterior surface of the til)ia, and 

 the internal lateral ligament of tlie ankle-joint. 



Posteriorly, it is covered by the skin and fascia, the gastrocnemius and soleus, 

 and th(^ deep or intermuscular fascia of the leg, by which it is tightly bound down 

 to the underlying nmscles. It is crossed by the posterior tibial nerve about an inch 

 and a half below its origin and after it has given off its peroneal branch, the nerve 

 first being on the inner, and for the rest of its course on the outer side of the vessel 

 (fig. 374). It is accompanied by two veins, which send numerous anastomosing 

 branches across it. In the lower third of the leg the artery is superficial, ])eing 

 only covered by the skin and hy the sujx'rficial and dee]) fascine. 



