POSTERIOR TIBIO-FIBULAR REGION. 



423 



Popliteus. 



Flexor Longus Pollicis. 



Deep Layer. 



Flexor Longus Digitorum. 

 Tibialis Posticus. 



Fig. 260. Muscles of the 

 Back of the Leg. Deep 

 Layers. 



Dissection. Detach the Soleus from its attachment to the 

 fibula and tibia, and turn it downwards when the deep layer of 

 muscles is exposed, covered by the deep fascia of the leg. 



The deep fascia of the leg is a broad, transverse, in- 

 termuscular septum, interposed between the super- 

 ficial and deep muscles in the posterior tibio-fibular 

 region. On each side it is connected to the margins 

 of the tibia and fibula. Above, where it covers the 

 Popliteus, it is thick and dense, and receives an ex- 

 pansion from the tendon of the Semimembranosus; it 

 is thinner in the middle of the leg ; but below, where 

 it covers the tendons passing behind the malleoli, it 

 is thickened. It is continued onwards in the interval 

 between the ankle and the heel, where it covers the 

 vessels, and is blended with the internal annular liga- 

 ment. 



This fascia should now be removed, commencing from below 

 opposite the tendons, and detaching it from the muscles in the 

 direction of their fibres. 



The Popliteus is a thin, flat triangular muscle, which 

 forms part of the floor of the popliteal space, and is 

 covered by a tendinous expansion, derived from the 

 Semimembranosus muscle. It arises by a strong flat 

 tendon, about an inch in length, from a deep depres- 

 sion on the outer side of the exteral condyle of the 

 femur, and from the posterior ligament of the knee- 

 joint ; and is inserted into the inner two-thirds of the 

 triangular surface above the oblique line on the pos- 

 terior surface of the shaft of the tibia, and into the 

 tendinous expansion covering the surface of the 

 muscle. The tendon of the muscle is covered by that 

 of the Biceps and the external lateral ligament of the 

 knee-joint ; it grooves the outer surface of the exter- 

 nal semilunar cartilage, and is invested by the syno- 

 vial membrane of the knee-joint. 



Relations. By its superficial surface, with the fascia 

 above mentioned, which separates it from the Gastroc- 

 nemius, Plantaris, popliteal vessels, and internal pop- 

 liteal nerve. By its deep surface, with the superior 

 tibio-fibular articulation, and back of the tibia. 



The Flexor Longus Pollicis is situated on the fibular 

 side of the leg, and is the most superficial and largest 

 of the three next muscles. It arises from the lower 

 two-thirds of the internal surface of the shaft of the 

 fibula, with the exception of an inch at its lowest 

 part ; from the lower part of the interosseous mem- 

 brane ; from an intermuscular septum between it and 

 the Peronei, externally ; and from the fascia covering 

 the Tibialis Posticus. The fibres pass obliquely 

 downwards and backwards, and terminate round a 

 tendon which occupies nearly the whole length of the posterior surface of the 

 muscle. This tendon passes through a groove on the posterior surface of the 



