FASCIA OF THE LEG. 259 



It is firmly attached to the tibia and fibula at each side, and be- 

 comes thickened inferiorly into a narrow band, the anterior annular 

 ligament, beneath which the tendons of the extensor muscles pass 

 into the dorsum of the foot in distinct sheaths, lined by synovial 

 bursae. Upon the outer side it forms a distinct sheath which enve- 

 lopes the peronei muscles, and ties them to the fibula. The anterior 

 annular ligament is attached by one extremity to the outer side of 

 the os calcis, and divides in front of the joint into two bands ; one of 

 which is inserted into the inner malleolus, while . the other spreads 

 over the inner side of the foot, and becomes continuous with the 

 internal portion of the plantar fascia. 



The fascia of the dorsum of the foot is a thin layer given off from 

 the lower border of the anterior annular ligament ; it is continuous 

 at each side with the lateral portions of the plantar fascia. 



The fascia of the posterior part of t fie leg is much thinner than the 

 anterior, and consists of two layers, superficial and deep. The 

 superficial layer is continuous with the posterior fascia of the thigh, 

 and is increased in thickness upon the outer side of the leg by an 

 expansion derived from the tendon of the biceps ; it terminates infe- 

 riorly in the external and internal annular ligaments. The deep 

 layer is stretched across between the tibia and fibula, and forms the 

 intermuscular fascia between the superficial and deep layer of mus- 

 cles. It covers in superiorly the popliteus muscle, receiving a tendi- 

 nous expansion from the semi-membranosus muscle, and is attached 

 to the oblique line of the tibia. 



The internal annular ligament is a strong fibrous band attached 

 above to the internal malleolus, and below to the side of the inner 

 tuberosity of the os calcis. It is continuous above with the posterior 

 fascia of the leg, and below with the plantar fascia, forming sheaths 

 for the passage of the flexor tendons and vessels, into the sole of the 

 foot. 



The external annular ligament, shorter than the internal, extends 

 from the extremity of the outer malleolus to the side of the os calcis, 

 and serves to bind down the tendons of the peronei muscles in their 

 passage beneath the external ankle. 



The plantar fascia consists of three portions, a middle and two 

 lateral. 



The middle portion is thick and dense, and is composed of strong 

 tendinous fibres, closely interwoven with each other. It is attached 

 posteriorly to the inner tuberosity of the os calcis, and terminates 

 under the heads of the metatarsal bones in five fasciculi. Each of 

 these fasciculi divides into two slips, which are inserted into each 

 side of the bases of the first phalanges of the toes, leaving an interval 

 between them for the passage of the flexor tendons. The point of 

 division of this fascia into fasciculi and slips, is strengthened by 

 transverse bands, which preserve the solidity of the fascia at its 

 broadest part. The intervals between the toes give passage to the 

 digital arteries and nerves and the lumbricales muscles. 





