102 THE SURGICAL ANATOMY OF THE HORSE 



Superficially to the popliteus, on the posterior aspect of the joint, is 

 placed the powerful tendon of origin of the flexor perforatus muscle 

 which arises from the floor of the supracondyloid fossa. Still more 

 superficially than the perforatus tendon are the tendons of origin of 

 the gastrocnemius. The outer of these arises from the outer lip of 

 the supracondyloid fossa and the inner from the supracondyloid 

 crest. 



Between the outer lip of the femoral trochlea and the outer condyle 

 is placed a well-marked pit, from which arises a very powerful tendon 

 which is common to the extensor pedis muscle and the tendinous or 

 superficial division of the flexor metatarsi. The tendon plays through the 

 notch which is situate between the anterior and external tuberosities of 

 the tibia. The tendon runs obliquely downwards and slightly inwards 

 to the outer side of, and a short distance behind, the external straight 

 ligament of the patella. Its play through the above-mentioned notch 

 is facilitated by an extensive diverticulum of the external synovial 

 membrane of the stifle, which envelops the tendon. The muscles to 

 which this tendon is common have very slight action on the stifle, their 

 function being to flex the hock and extend the interphalangeal joints. 



The outer aspect of the stifle is clothed by the thin aponeurotic 

 insertions of the tensor vagins femoris and biceps femoris muscles. 



Blood Supply 



The Popliteal Artery. — This vessel is the direct continuation of the 

 femoral, the name popliteal being given to the vessel after it has passed 

 between the two heads of the gastrocnemius muscle. The vessel next 

 passes under the popliteus muscle, and crosses the posterior surface of the 

 posterior common ligament obliquely downwards and outwards to the 

 tibio-fibular arch, where it divides to form the anterior and posterior 

 tibial arteries. As the vessel crosses the upper portion of the ligament it 

 gives off^ two or three small branches, which penetrate the ligament 



