THE COMMON PERONEAL NERVE 1013 



The muscular branches arise from the commencement of the nerve and are dis- 

 tributed to the abductor digiti quinti and quadratus plantse. 



The articular branches supply the calcaneo-cuboid joint. 



The superficial branch supplies muscular filaments to the flexor digiti quinti 

 brevis, the opponens, the third plantar and fourth dorsal interosseous muscles, 

 and divides into two common plantar digital nerves, each of which subdivides to 

 form proper plantar digital nerves. 



The lateral of the two common branches supplies the lateral side of the fifth digit; the medial 

 connects with the lateral digital branch of the medial plantar nerve (fig. 772) and divides into 

 proper plantar digital nerves for the adjacent sides of the fourth and fifth digits. The digital 

 branches of the superficial division of the lateral plantar, like those of the medial plantar, supply 

 the skin of the toes and the beds of the nails, and their fibres terminate in numerouos Pacinian 

 corpuscles. 



The deep branch passes forward and medialward into the deep part of the 

 sole with the plantar arterial arch. It runs deep to the quadratus plantae, the long 

 flexor tendons and the lumbricals, and the oblique adductor of the great toe. It 

 lies, therefore, immediately beneath the bases of the metatarsal bones and it 

 supplies the following muscular and articular branches: — 



Muscular branches to the lateral three lumbricals, the interossei of the medial three inter- 

 metatarsal spaces, and the transverse and oblique adductor muscles of the great toe. 



Articular branches to the intertarsal and to the tarso-metatarsal joints and not uncommonly 

 to the metatarso-phalangeal joints also. Filaments from the deep branch frequently pass 

 through the interosseous spaces and join with the interosseous branches of the deep peroneal 

 (anterior tibial) nerve. 



The common peroneal (external popliteal) nerve. — At the apex of the pop- 

 liteal space, where the two component parts of the sciatic trunk usually become 

 distinct, the lateral portion receives the name common 'peroneal nerve. It de- 

 scends along the posterior border of the biceps femoris, which forms the upper part 

 of the lateral boundary of the space (fig. 771). It leaves the space at the lateral 

 angle, crosses the plantaris, the lateral head of the gastrocnemius, the pop- 

 liteus, and the inferior external artery, and descends behind the upper part of the 

 soleus, to the neck of the fibula, where it turns forward between the peroneus 

 longus and the bone, and breaks up into its three terminal branches, the recurrent 

 articular, the superficial peroneal (musculo-cutaneous), and the deep peroneal 

 (anterior tibial) nerves (fig. 773). 



Upper branches. — While it is in the popliteal space the common peroneal 

 (external popliteal) nerve gives off two articular branches and a cutaneous branch. 



The superior articular branch accompanies the superior external articular artery. The 

 lateral head of the gastrocnemius, and it joins the inferior external articular artery behind the 

 tendon of the biceps femoris. Both the upper and lower articular branches pierce the ligaments 

 and are distributed in the interior of the knee joint. 



The cutaneous branch {communicans fibularis) , lateral sural cutaneous, is extremely variable 

 both as to the number of its branches and as to the place of its anastomosis with the medial 

 sural cutaneous. Leaving the common peroneal (external popliteal) in the popliteal space, it 

 descends between the deep fascia and the lateral head of the gastrocnemius to the middle of 

 the calf, where it pierces the fascia and unites with the medial sural cutaneous to form the 

 sural (external saphenous) nerve. In its course it may give off no branches; or it may give off 

 several, some of which supply the skin of the dorsum of the leg, while one of them, the peroneal 

 anastomotic branch, unites with the medial sural cutaneous to form the sural (short saphenous) 

 nerve. The junction of the peroneal anastomotic branch with the medial sural cutaneous may 

 take place at any point between the pophteal space and the lower third of the leg. 



The sural (external or short saphenous) nerve is formed by the union of the 

 lateral sural cutaneous nerve either directly, or tlu-ough a connecting branch, 

 the peroneal anastomotic, with the medial sural cutaneous (fig. 771). It descends 

 along the lateral border of the tendo Achillis, giving branches to the lower and 

 lateral part of the leg, and lateral calcaneal branches to the lateral side of the heel. 

 It passes dorsal to the lateral malleolus, turns forward across the lateral surface of 

 the cruciate (external annular) ligament, and becomes the lateral dorsal cutaneous 

 nerve. Continuing along the lateral side of the foot it divides into two branches, 

 the dorsal digitals, one of which supplies the lateral side of the fifth digit, while the 

 other anastomoses with or takes the place of a branch of the superficial peroneal 

 (musculo-cutaneous) nerve, which is distributed to the adjacent sides of the fourth 

 and fifth digits (fig. 773). 



The terminal branches of the common peroneal. — (1) The recurrent articular 

 nerve passes medialward, around the neck of the fibula, and through the upper 



