2SO A MANUAL OF ANATOMY 



The Fibula. 



The fibula, or peroneal bone, is situated on the outer side of the 

 tibia. It is very slender for its length, and is a rudimentary bone. 

 It takes no part in transmitting the weight of the body, but serves 

 chiefly to afford attachment to muscles, though it also forms part 

 of the ankle-joint, and acts as a brace or support to the tibia. It 

 is a long bone, and is divisible into a shaft and two extremities, 

 upper and lower. 



The upper extremity, or head, is enlarged and knob-like, its upper 

 surface being somewhat flattened and sloping. It is situated about 

 f inch below the level of the head of the tibia. Posteriorly it is 

 prolonged upwards into the styloid process, to the tip of which the 

 short external lateral ligament of the knee-joint is attached. In front 

 of this process the upper surface of the head is sloped downwards 

 and forwards, and is divisible into an articular and a non-articular 

 part. The articular division is internal in position, and takes the 

 form of a flat circular facet, which is directed upwards, inwards, and 

 forwards, to articulate with the facet on the posterior and under 

 aspect of the external tuberosity of the tibia, by which latter it 

 is overhung. The non-articular division is external in position, and 

 takes the form of a rough depression, into which the tendon of the 

 biceps femoris, previously divided into two parts by the long 

 external lateral ligament, takes insertion. Posteriorly the head 

 gives origin to the soleus. Externally it gives origin to the peroneus 

 longus, and at a point nearly ^ an inch anterior to the styloid 

 process its outer margin gives attachment to the long external 

 lateral ligament. Anteriorly it gives origin to the extensor longus 

 digitorum. The constricted part below the head is called the 

 neck. 



The upper extremity presents several nutrient foramina for 

 branches of the inferior external articular of the popliteal, and 

 superior fibular of the anterior tibial, arteries. 



The lower extremity is prolonged downwards into a massive pro- 

 jection, called the external malleolus, which is not only larger, but 

 lower down and farther back, than the internal malleolus. It 

 is triangular or pyramidal, the base being directed upwards. 

 The external surface is rough, convex, and subcutaneous. The 

 internal surface is divisible into two parts, articular and non- 

 articular. The articular division is anterior in position, and occupies 

 about two-thirds of the surface. It is triangular and convex, and 

 it mainly articulates with the outer surface of the astragalus. 

 Superiorly, however, for about \ inch, it assumes a some- 

 what semilunar outline, and this portion articulates with the 

 outer aspect of the tibia. The non-articular division is posterior 

 in position, and occupies about one-third of the surface. It is 

 rough, depressed, and triangular, and is known as the digital fossa. 

 Superiorly it gives attachment to the transverse ligament of the 

 inferior tibio-fibular joint, and interiorly to the posterior fasciculus 



