THE LEG 475 



has a short muscular belly ending in a long, thin tendon, which is inserted into 

 the calcaneus on the medial side of the tendo calcaneus. 



These three muscles receive their nerve-supply from the tibial (internal 

 popliteal) nerve (L. 4, 5, S. i and 2), and they act as extensors of the ankle- 

 joint. In addition, the gastrocnemius and plantaris assist in flexing the knee- 

 joint. 



Both the tendo calcaneus and the plantaris tendon may be 

 ruptured by violent muscular efforts ; in the case of the former 

 the tendon is exposed by a longitudinal incision, and the torn 

 ends are sutured together. Occasionally, instead of rupturing, 

 the tendo calcaneus tears off a fragment from the postero- 

 superior part of the calcaneus fracture by avulsion (Fig. 146). 

 In this case the incision lies along the lateral border of the 

 tendon and curves forwards along the lateral surface of the 

 calcaneus. In order to approximate the fragments it may be 

 necessary to lengthen the tendon, and this may be effected by 

 a series of hemi-divisions along each border. The fragment is 

 then screwed into place and the foot is put up in a plaster case, 

 with the knee flexed and the toes pointed so as to relax the 

 gastrocnemius and the soleus as far as possible. 



The Deep Group of Muscles is separated from the superficial group by 

 a strong layer of the deep fascia, which extends from the posterior border 

 of the fibula to the medial border of the tibia. 



The Tibialis Posterior arises from the posterior surface of the interosseous 

 membrane and the adjoining parts of the tibia and fibula. Its tendon passes 

 distally and medially, and, as it grooves the medial malleolus, passes through 

 a separate compartment of the laciniate ligament. It is mainly inserted into 

 the navicular tuberosity ; but, in addition, it sends strong slips to all the 

 other tarsal bones and to the bases of the middle three metatarsals. These 

 slips strengthen the plantar ligaments of the foot and assist in maintaining 

 the longitudinal and transverse arches (p. 492). 



The Flexor Digitorum Longus arises from the posterior surface of the 

 tibia, medial to the tibialis posterior. It inclines slightly laterally as it 

 descends, and, where it passes through the laciniate ligament, it lies lateral 

 to the tibialis posterior tendon. 



The Flexor Hallucis Longus arises from the posterior surface of the 

 fibula, lateral to the tibialis posterior. Opposite the ankle-joint it passes 

 through a separate compartment of the laciniate ligament, being separated 

 from the flexor digitorum longus tendon by the tibial nerve and the posterior 

 tibial vessels. 



All three muscles are supplied by the tibial nerve (L. 5, S. i and 2). They 

 act as extensors of the ankle-joint, but, in addition, the tibialis posterior 

 inverts the foot, while the other two flex the toes. 



The Posterior Tibial Artery arises from the popliteal at 

 the distal border of the popliteus and descends between the 

 deep muscles and the fascia which covers them. It may be 

 mapped out on the surface of the limb by a line drawn from the 

 middle of the popliteal fossa to the mid-point between the 



