THE LEG 471 



upper surface of the calcaneus (p. 478). These ligaments are 

 split by the tendons of the anterior compartment of the leg. 

 The transverse ligament possesses two compartments, of which 

 the medial is occupied by the tibialis anterior and the lateial 

 by the extensor hallucis longus, the extensor digitorum longus, 

 and the peronseus tertius. A similar arrangement exists at the 

 cruciate ligament, with the exception that the extensor hallucis 

 longus possesses a separate compartment, intermediate in 

 position between the other two. As the tendons traverse the 

 ligaments, they are surrounded by synovial sheaths, which 

 extend for variable distances upon them. 



On the medial side of the ankle-joint the deep fascia is 

 thickened to form the laciniate (internal annular) ligament) 

 which holds in place the tendons of the tibialis posterior, the 

 flexor digitorum longus, and the flexor hallucis longus. Synovial 

 sheaths enclose these tendons, as they lie under the ligament, 

 and extend forwards along them into the sole of the foot. 



Two similar bands are placed on the lateral side of the ankle 

 in relation to the tendons of the peronaeus longus and brevis. 

 The superior retinaculum lies behind the lateral malleolus and 

 possesses a single compartment, lined by a common synovial 

 sheath. The inferior retinaculum extends from the tip of the 

 lateral malleolus to the lateral aspect of the calcaneus below 

 the trochlear process. It possesses two compartments separated 

 by the process and lined by synovial sheaths which are continuous 

 with the common sheath under the superior retinaculum. 

 Either retinaculum may be ruptured by violent contraction 

 of the peronaei, and the tendons are subsequently easily 

 displaced. 



Anterior Compartment of the Leg. The Tibialis Anterior arises from 

 the proximal two-thirds of the lateral surface of the tibia and the adjoining 

 part of the interosseous membrane. Its tendon runs distally and medially, 

 passing behind the transverse and cruciate ligaments, to be inserted into the 

 medial side of the base of the first metatarsal and the adjoining part of the 

 medial cuneiform. The muscle acts as a flexor of the ankle and an inverter 

 of the foot. It is supplied by the deep peroneal (ant. tibial) nerve (L. 4, 5, 

 and S. i). 



The Extensor Digitorum Longus, the Extensor Hallucis Longus, and the 

 Peronceus Tertius arise from the fibula and occupy the lateral part of the 

 anterior compartment. The former two are inserted into the distal phalanges ; 

 they flex the ankle-joint and extend the toes. The peronseus tertius is in- 

 serted into the dorsum of the base of the fifth metatarsal ; it flexes the ankle- 

 joint and everts the foot. All three are supplied by the deep peroneal (anterior 

 tibial) nerve (L. 4, 5, and S. i). 



The Anterior Tibial Artery arises from the popliteal at the 



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