Fig. 187. Outer Aspect of Leg. External Popliteal Nerve. 



On the outer side a larger window has been cut out of the fascia; portions 



have been removed from the following muscles: Anterior Tibial, Long Extensor 



of the Toes, Long Extensor of the Big Toe, Long and Short Peroneal Muscles, 



so that portions of the Tibia and Fibtda have been exposed. 



The Anterior Aspect of the Leg is occupied b\' the Extensor Muscles of 

 the Foot; the External Surface of the Tibia is covered b)' the Anterior Tibial 

 Muscle and the Long Extensor of the Toes. About the middle of the leg, the 

 Long Extensor of the Big Toe appears between these two muscles and in these 

 relations the Tendons pass under the Annular Ligament, on to the Dorsum of 

 the Foot. 



On the outer side, the 2 Peroneal Muscles which arise from the Fibula 

 pass down, as tendons, behind the Outer Malleolus. The large Vessels and Nerves 

 are on the Flexor Aspect (cf. all large joints). Their branches to supply the 

 anterior aspect of the leg pass to the front from the Popliteal Space b}' various 

 routes. The Anterior Tibial Artery passes directly forwards over the upper margin 

 of the Interosseous Membrane, and runs downwards upon this Membrane lying at 

 first between the Anterior Tibial Muscle and Long Extensor Muscle of the Toes, 

 then between the former and the Long Extensor Muscle of the Big Toe. In the 

 lower third this tendon crosses the Artery obliquely, so that finally the Artery 

 reaches the Dorsum of the Foot by passing below the Anterior Annular Ligament 

 between the Long Extensor Muscles of the Toes and Big Toe. 



The External Popliteal Nerve takes quite a different course, coming off 

 the Great Sciatic Nerve at or above the middle of the thigh this nerve passes 

 towards the outer boundary of the Popliteal Space and perforating the Long 

 Peroneal Muscle winds around the head of the Fibula and appears on the anterior 

 aspect of the Leg. In its course this nerve divides into a Superficial and a Deep 

 branch; the former — Musculo-Cutaneous Nerve supplies the Peroneal Muscles 

 and pierces the deep fascia at the junction of the middle and lower thirds of the 

 Leg, whence it runs down to the Dorsum of the Foot as a Cutaneous Nerve. 

 The Anterior Tibial Nerve passes obliquely through the Origin of the Long 

 Extensor Muscle of the Toes, and runs downwards on the outer side of the 

 Artery; lower down the Nerve crosses in front of the Artery and lies antero- 

 internal to it at the ankle-joint. In its course it supplies the three Extensors on 

 the front of the Leg. 



The position of the External Popliteal Nerve passing round the head of 

 the Fibula requires great care in operations on the upper end of the Fibula 

 because a deep longitudinal incision would divide the nerve. 



