498 A MANUAL OF ANATOMY 



The part of the fascia behind the knee-joint presents an opening 

 for the passage of the short saphenous vein. In the region of the 

 gastrocnemius and over the inner surface of the tibia the deep fascia 

 is very thin. Over the front and outer parts of the leg, however, 

 more especially in the upper half, it attains considerable strength 

 and density, and there it gives origin by its deep surface to the super- 

 ficial fibres of the muscles which it covers. In the region of the 

 knee-joint it receives many strong accessions of fibres from the 

 tendons of the quadriceps extensor cruris, biceps femoris, sartorius, 

 gracilis, and semitendinosus. 



Four expansions are given off from its deep surface, whkh are 

 called intermuscular septa — anterior, antero - external, postero- 

 external, and posterior or transverse. The anterior intermuscular 

 septum is limited to the upper third of the leg, where it extends 

 between the tibialis anticus and extensor longus digitorum, to both 

 of which muscles it gives partial origin. The antero -external inter- 

 muscular septum is attached to the antero-external border of the 

 fibula, and extends between the extensor longus digitorum and 

 peroneus tertius on the anterior surface, and the peroneus longus 

 and peroneus brevis on the external surface. The postero-external 

 intermuscular septum is attached to the postero-external border 

 of the fibula, where it extends between the peroneus longus and 

 peroneus brevis on- the external surface, and the soleus and flexor 

 longus hallucis on the posterior surface. The peroneus longus 

 and peroneus brevis are thus completely shut off from the adjacent 

 muscles by the two external intermuscular septa. These septa, 

 along with the deep fascia at the surface and the external surface 

 of the shaft of the fibula, form a long fibro-osseous canal which 

 contains the peroneus longus and peroneus brevis. The posterior 

 or transverse intermuscular septum is a broad expansion which 

 passes transversely between the postero-external border of the 

 fibula and the internal border of the tibia. It lies beneath the 

 soleus and upon the deep muscles of the back of the leg, as well 

 as upon the posterior tibial vessels and nerve, binding down the 

 structures which it covers. 



Annular Ligaments. — These are situated in the region of the 

 ankle-joint, and are thickened portions of the deep fascia. They 

 serve to confine and maintain in position the strong tendons in that 

 vicinity, and are three in number — external, internal, and anterior. 



The external annular ligament extends between the posterior 

 border of the external malleolus and the outer border of the tuber 

 calcis and adjacent portion of its outer surface. Its direction is 

 downwards and backwards over the peroneal groove behind the 

 external malleolus. The tendons of the peroneus longus and 

 peroneus brevis pass beneath it, and are thereby kept in position. 

 The tendon of the peroneus brevis is close to the bone, and that of 

 the peroneus longus is directly behind the brevis tendon, both 

 being invested by one common synovial sheath. The external 

 annular ligament at its anterior border is continued forwards to 



