3 io THE INFERIOR EXTREMITY 



from its posterior aspect and descends between the two heads 

 of the gastrocnemius. Follow that branch to the distal angle 

 of the fossa, dividing the popliteal fascia superficial to it. The 

 articular branches are three in number, superior medial genicular, 

 inferior medial genicular, and middle genicular. All three 

 branches spring from the medial side of the tibial nerve, the 

 superior branch at or above the proximal angle of the fossa, and 

 the other two at more distal levels. Each joins a corresponding 

 branch of the popliteal artery, and is distributed with it. The 

 superior branch leaves the fossa above the medial condyle of 

 the femur, the inferior branch turns medially below the medial 

 condyle of the tibia, and the middle branch pierces the posterior 

 ligament of the knee joint. The muscular branches arise about 

 the middle of the fossa and pass to the two heads of the gastro- 

 cnemius, the plantaris, the soleus, and the popliteus ; the heads 

 of the gastrocnemius must be separated to obtain a proper view 

 of these branches. The branch to the soleus will be recognised 

 because it passes between the plantaris and the lateral head of 

 the gastrocnemius. The nerve to the popliteus lies deeply in 

 the angle between the heads of the gastrocnemius superficial 

 to the popliteal artery. It will be followed to its termination 

 in a subsequent dissection (see p. 403). 



When the tibial nerve and its branches have been cleaned 

 return to the proximal angle of the fossa, dissect in the fat lateral 

 to the tibial nerve at the medial border of the biceps, and secure 

 the common peroneal nerve. It descends along the medial 

 border of the biceps, and leaves the fossa at the lateral angle, 

 crossing superficial to the plantaris and the lateral head of the 

 gastrocnemius (Fig. 132). Follow the nerve carefully from 

 above downwards. Whilst it is in the fossa it gives off two 

 articular branches, superior lateral genicular, and inferior 

 lateral genicular, and a cutaneous branch, the anastomolic 

 peroneal nerve, which crosses the lateral head of the gastro- 

 cnemius. As the common peroneal nerve lies superficial to 

 the lateral head of the gastrocnemius it gives off the lateral 

 cutaneous nerve of the calf; then it passes posterior to the head of 

 the fibula, from which it is separated by the highest fibres of 

 the soleus, and disappears between the peroneus longus and the 

 neck of the fibula. The superior lateral articular branch leaves 

 the fossa proximal to the lateral condyle of the femur with the 

 corresponding branch of the popliteal artery. The inferior 

 lateral articular branch joins the inferior lateral genicular 

 branch of the popliteal artery at the lateral side of the knee 

 between the head of the fibula and the lateral condyle of the 

 femur. The lateral cutaneous nerve of the calf and the anasto- 

 motic peroneal cutaneous branch sometimes arise from the 

 common peroneal nerve by a common stem (see Fig. 132). 

 When the nerves mentioned have been found and cleaned, clean 

 the two heads of the gastrocnemius and separate the plantaris 

 from the medial border of the lateral head, taking care not to 

 injure the nerve to the soleus which passes between the plantaris 

 and the lateral head of the gastrocnemius. As the muscles are 

 cleaned, note the branches of the popliteal artery which pass to 

 them, but divide those branches if they interfere with the separa- 

 tion of the muscles. 



The popliteal vein and its tributaries and the popliteal artery 



