THE REGION OF THE KNEE. 



FIG. 83. The popliteal space. 



FIG. 84. The knee-joint after the injection of a blue mass into the articular cavity; the bursas communicating with 

 the joint are also filled with the blue injection. The non-communicating bursas have been injected with a red mass. 



(From a Berlin model.) 



The superficial structures of the popliteal space are the short saphenous vein and nerve 

 (Fig. 83). The short saphenous vein lies upon the deep fascia. It arises behind the external 

 malleolus, runs upward upon the muscles of the calf in the furrow between the two heads of the 

 gastrocnemius, perforates the deep fascia in the popliteal space, and empties into the popliteal 

 vein. It usually gives off a branch which runs to a higher level and empties into the vena pro- 

 funda femoris. To the outer side of the vein the short saphenous nerve runs downward as far 

 as the external border of the foot. This nerve arises upon or beneath the deep fascia in the 

 popliteal space or lower down by the union of the communicans poplitei (n. cutaneus surae medialis), 

 from the internal popliteal nerve, with the communicans peronei (n. cutaneus surae lateralis), 

 from the peroneal nerve. To the inner side of the knee is the internal (or long) saphenous vein, 

 and somewhat posterior to this structure the long saphenous nerve makes its appearance be- 

 neath the tendon of the sartorius muscle (see page 161). In the median line of the popliteal 

 space the internal popliteal nerve may be felt, and even seen in spare individuals, when the knee 

 is extended; it is the motor nerve of the flexor surface and gives off branches to the heads of the 

 gastrocnemius muscle in this situation. Somewhat deeper and closely associated with the nerve 

 upon its inner side is the popliteal vein, and still deeper and more internal is the popliteal artery. 

 The popliteal artery makes its appearance at the opening in the adductor magnus and lies first 

 upon the posterior surface of the vastus internus and then upon the planum popliteum, though 

 it is separated from this bony surface by a small quantity of fat ; lower down the vessel is inti- 

 mately related with the capsular ligament of the joint, so that it will be readily understood that 

 the artery and its accompanying vein must suffer compression in posterior dislocations at the 

 knee, and that this relation must always be borne in mind in resections of the articulation. It 

 is also clear that in supracondyloid fractures of the lower end of the femur in which the lower 

 fragment is tilted backward by the gastrocnemius muscle disagreeable symptoms will be pro- 

 duced by the laceration of the popliteal vessels and of the internal popliteal nerve. The artery 

 finally runs upon the popliteus muscle, at the inferior margin of which it divides into its terminal 

 branches, the anterior and posterior tibial arteries. In addition to the numerous branches to 

 the muscles in this region, of which the large sural arteries to the heads of the gastrocnemius 

 should be particularly emphasized, the popliteal gives off five articular arteries, which vary in 

 size and aid in the formation of the rete articulare. There are two superior and two inferior 

 articular arteries (an external and an internal of each), and an azygos articular (a. articularis 

 genu media) which passes into the interior of the joint. 



The peroneal nerve (external popliteal) (Fig. 83) follows the inner border of the biceps 

 muscle and gradually becomes more distant from the internal popliteal nerve; at the head of 

 the fibula it enters the peroneus longus muscle and immediately divides into its two main branches, 

 the musculocutaneous and the anterior tibial nerves. 



Knee-joint. The study of the knee-joint (Fig. 84) should be preceded by a review of the 

 following parts: At the lower end of the femur, the condyles, the epicondyles, the fossa inter- 



