440 A MANUAL OF ANATOMY 



and internal popliteal nerves. Under these circumstances the 

 external popliteal nerve often pierces the pyriformis. 



Popliteal Space. — ^The pophteal space or ham* is situated behind 

 the knee-joint, whence it extends upwards to the junction of the 

 upper three-fourths and lower fourth of the thigh, and down- 

 wards to the junction of the upper sixth and lower five-sixths of 

 the leg. In shape the space resembles a diamond. 



Boundaries. External — (a) Above the Knee-joint. — Biceps femoris. 

 {h) Below the Knee-joint. — External head of the gastrocnemius, and 

 plantaris. 



Internal — {a) Above the Knee-joint. — Semitendinosus, semimem- 

 branosus, gracilis, sartorius, and tendon of the adductor magnus, 

 in the order named from behind forwards, (b) Below the Knee- 

 joint. — Internal head of the gastrocnemius. 



The superior median angle of the space corresponds with the 

 divergence of the hamstring muscles, the inferior median angle 

 by the approximation of the external and internal heads of the 

 gastrocnemius, the external angle by the meeting between the 

 biceps femoris and external head of the gastrocnemius, and the 

 internal angle by the meeting between the semimembranosus and 

 internal head of the gastrocnemius. 



The roof is formed by the integument. It contains the small 

 sciatic nerve, and, in its lower part, the terminal portion of the 

 external or short saphenous vein. 



The floor is formed, from above downwards, by the popliteal 

 surface or trigone of the femur, the posterior ligament of the knee- 

 joint, and the popliteus muscle, covered by the popliteal fascia. 



Contents. — The contents are the popliteal artery and its branches, 

 the popliteal vein and its tributaries (including the termination of 

 the external or short saphenous vein), the internal popliteal nerve 

 and its branches, the external popliteal nerve and some of its 

 branches, the geniculate branch of the obturator nerve (inconstant), 

 lymphatic glands, and a large amount of fat. 



Popliteal Artery. — This vessel is the continuation of the femoral 

 artery. It extends from the posterior margin of the femoral 

 opening, which is in connection with the adductor magnus, to the 

 lower border of the popliteus muscle, where it divides into anterior 

 and posterior tibial arteries. The division takes place on a level ; 

 with the lower border of the tubercle of the tibia, and fully , 

 i| inches below the level of the upper surface of the head of that j 

 bone. The vessel at first passes downwards and outwards until it j 

 reaches the middle line of the limb. It then takes a straight course 

 downwards between the condyles of the femur, and finally it sinks! 



* The word ham is derived from a Teutonic verb signifying ' to be curved; 

 or crooked,' and it has been appUed to the popUteal space because that space' 

 is situated behind the ' crook,' ' curve,' or bend of the knee. By a later; 

 extension of the word ham it came to be appUed to the whole of the back of 

 the thigh — hence the name hamstring, which is given to the muscles of that 

 region. 



