MUSCLES OF THE LEG. 



137 



of the fracture is found in a violent twist of 

 the ankle with dislocation, the deformity occa- 

 sioned by this state of the joint is more or less 

 considerable, according to the degree of this 

 displacement. 



(A. T. S. Dodd.) 



MUSCLES OF THE LEG. The muscles 

 lying on the bones of the leg, both before and 

 behind, are, with the exception of one, pro- 

 perly muscles of the ankle-joint and foot, since 

 their primary action is exclusively upon these 

 parts. (See article FOOT, MUSCLES OF.) For 

 the convenience, however, of description they 

 will here be demonstrated according to their si- 

 tuation. 



The muscles of the leg may be classed into 

 anterior, external, and posterior. The anterior 

 lying in the space between the tibia and fi- 

 bula are four in number, consisting of tibialis 

 anticus, extensor proprius pollicis, extensor 

 longus digitorum, and peroneus tertius. The 

 tibialis anticus and extensor longus alone are 

 seen at the upper part of the leg on removing 

 the deep fascia ; the extensor proprius pol- 

 licis emerging from between these muscles 

 about one-third down the leg, and the peroneus 

 tertius shewing itself as a separate slip of the 

 extensor longus, about the same height, and at 

 its fibular side. 



1. Tibialis (tnlicus lies upon the fibular and 

 anterior surface of the tibia; arises, principally 

 muscular, from the fibular side of the tibia, 

 through its two upper thirds, from its tuber- 

 osity and spine, and from a small portion of 

 the interosseous ligament, from the fascia of 

 the leg, and from an aponeurotic septum placed 

 between it and the extensor digitorum longus. 

 The muscle is larger above than below; its 

 fleshy fibres converge to a strong tendon which 

 crosses from the outside to the fore part of the 

 tibia, passes through a distinct ring of the 

 annular ligament near the ankle, runs over the 

 astragalus and os naviculare, and is inserted 

 into the upper part of the os cuneiforme in- 

 ternum, and base of the metatarsal bone of the 

 great toe. The insertion of the tendon is con- 

 cealed in part by the adductor and flexor brevis 

 of the great toe. Between the tendon of this 

 muscle and the os cuneiforme we find a small 

 bursa mucosa. This muscle is covered in front 

 by the fascia of the leg, to which it adheres 

 superiorly ; behind it is in contact with the 

 tibia and interosseous ligament, on the fibular 

 side with the extensor digitorum communis, 

 and extensor proprius pollicis. Its action is to 

 flex the foot upon the leg by elevating the an- 

 terior part of the foot. 



2. Extensor longns digitorum. This mus- 

 cle occupies the fibular side of the tibio-fi- 

 bular fossa, as the last filled the inner side. 

 This is a tapering muscle also; it arises ten- 

 dinous and muscular from the fibular or 

 outer part of the head of the tibia, from the 

 head of the fibula, and from the anterior angle 

 of that bone almost its whole length, and from 

 part of the tibial side of it also ; it also takes 

 origin from the interosseous ligament, from the 

 fascia of the leg, and from the aponeurotic 



septum situated between this muscle and the 

 last. Below the middle of the leg it splits 

 into four tendons. These pass under the ante- 

 rior annular ligament in one common sheath 

 with the peroneus tertius. They then run along 

 the dorsum of the foot, spreading as they go, 

 and are inserted into the root of the first pha- 

 lanx of each of the four smaller toes. To- 

 wards their termination each of ihe tendons ex- 

 pands into an aponeurosis, covering the upper 

 surface of the phalanges, and this is strengthened 

 by the tendons of the extensor brevis and gives 

 attachment to the lumbricales and interossei. 



This muscle is covered in front by the fascia 

 of the leg, the annular ligament and the in- 

 tegument; posteriorly it rests upon the fibula, 

 the interosseous ligament, and the tibia; exter- 

 nally it is in relation with the peronei muscles, 

 internally with the tibialis anticus, and extensor 

 proprius pollicis; along its lower and fibular 

 border lies the peroneus tertius. On the dor- 

 sum of the foot its four tendons cross obliquely 

 over those of the flexor brevis digitorum. 



Action. To extend all the joints of the four 

 smaller toes, and to bend the ankle-joint. 



3. Extensor proprius pollicis lies between 

 the two last muscles. Its origin is hidden by 

 them. It commences about one-third down 

 the leg, from the smooth surface of the fibula, 

 between the anterior and tibial angles of that 

 bone, of which surface it occupies part, through 

 the middle third of its length, also from the 

 lower two-thirds of the interosseous ligament. 

 The fleshy fibres run obliquely forward into a 

 tendon placed at the anterior border of the 

 muscle, which after passing beneath the an- 

 terior annular ligament, and along the dorsum 

 of the foot, is inserted into the bases of the 

 first and second phalanges of the great toe. 



Action. To extend the great toe, and to 

 bend the ankle. 



By its fibular side this muscle is in relation 

 with the extensor digitorum communis ; by its 

 inner side with the tibialis anticus and anterior 

 tibial vessels. The anterior border is covered 

 by these two muscles, as low as about the 

 middle of the leg, and inferiorly by the anterior 

 annular ligament, under which it passes in a 

 separate groove, and by the integuments. The 

 posterior border rests upon the fibula and in- 

 terosseous ligament, and it crosses in its course 

 over the lower end of the tibia the ankle-joint, 

 the anterior tibial vessels, and dorsum of the 

 foot. 



4. Peroneus tertius. This, which is in fact 

 a mere slip of the extensor digitorum com- 

 munis, and is situated on its fibular side, is so 

 closely connected with it at its origin that it 

 can with difficulty be separated. It arises 

 from the lower third of the fibula, being at- 

 tached to the anterior border and inner surface 

 of the bone ; also from the interosseous liga- 

 ment, and from an aponeurosis which connects 

 it on the outer side with the peroneus brevis. 

 It is inserted by a flat tendon into the fibular 

 side of the base of the metatarsal bone of the 

 little toe. Its action is to assist in flexing the 

 foot upon the leg. 



It is in contact with the fascia of the leg 



