The fibula (Calf Bone) is a bone placed on the lateral side of the tibia, with which it is connected above and below. It is the smaller of the two bones, and, in proportion to its length, the most slender of all the long bones. Its upper extremity is small, placed toward the back of the head of the tibia, below the level of the knee-joint, and excluded from the formation of this joint. Its lower extremity inclines a little forward, so as to be on a plane anterior to that of the upper end; it projects below the tibia, and forms the lateral part of the ankle-joint. The bone has a body and two extremities.
The Upper Extremity or Head
('capitulum fibul; proximal extremity')
The upper extremity is of an irregular quadrate form, presenting above a flattened articular surface, directed upward, forward, and medialward, for articulation with a corresponding surface on the lateral condyle of the tibia. On the lateral side is a thick and rough prominence continued behind into a pointed eminence, the apex (styloid process), which projects upward from the posterior part of the head. The prominence, at its upper and lateral part, gives attachment to the tendon of the Biceps femoris and to the fibular collateral ligament of the knee-joint, the ligament dividing the tendon into two parts. The remaining part of the circumference of the head is rough, for the attachment of muscles and ligaments. It presents in front a tubercle for the origin of the upper and anterior fibers of the Peronæus longus, and a surface for the attachment of the anterior ligament of the head; and behind, another tubercle, for the attachment of the posterior ligament of the head and the origin of the upper fibers of the Soleus.
Figure 1 : Lower extremity of right fibula. Medial aspect. |
Figure 2 : Plan of ossification of the fibula. From three centers. |
Surfaces
The anterior surface is the interval between the antero-lateral and antero-medial borders. It is extremely narrow and flat in the upper third of its extent; broader and grooved longitudinally in its lower third; it serves for the origin of three muscles: the Extensor digitorum longus, Extensor hallucis longus, and Peronæus tertius. The posterior surface is the space included between the postero-lateral and the postero-medial borders; it is continuous below with the triangular area above the articular surface of the lateral malleolus; it is directed backward above, backward and medialward at its middle, directly medialward below. Its upper third is rough, for the origin of the Soleus; its lower part presents a triangular surface, connected to the tibia by a strong interosseous ligament; the intervening part of the surface is covered by the fibers of origin of the Flexor hallucis longus. Near the middle of this surface is the nutrient foramen, which is directed downward. The medial surface is the interval included between the antero-medial and the postero-medial borders. It is grooved for the origin of the Tibialis posterior. The lateral surface is the space between the antero-lateral and postero-lateral borders. It is broad, and often deeply grooved; it is directed lateralward in the upper two-thirds of its course, backward in the lower third, where it is continuous with the posterior border of the lateral malleolus. This surface gives origin to the Peronæi longus and brevis.Figure 3 : Left calcaneus, superior surface. |
Figure 4 : Left calcaneus, inferior surface. |
- See also : Articulations between the Tibia and Fibula