The superior extremity is flattened from before backwards. The neck is not well marked. The great trochanter is very prominent, and projects beyond the level of the head of the femur. We divide the great trochanter into three parts: the summit, which is the most elevated portion; the convexity, which is situated in front; and the crest, formed by muscular impressions, situated outside and below the convexity. The digital fossa is situated behind and below the summit of the great trochanter. With regard to the lesser trochanter, it is placed so far down that it really forms part of the shaft of the bone, with which, besides, we have described it.
On the inferior extremity of the femur are two condyles and a trochlea; the condyles are clearly separated from this latter by a marked constriction.
The trochlea is directed with a slight obliquity downwards and inwards; its internal lip is much thicker and more prominent than the external; this is, accordingly, a condition exactly the opposite of that which characterizes the corresponding region of the human femur.
The knee-cap is lozenge-shaped; its superior angle projects upward, and produces a prominence at the part which corresponds to the base of the human patella, the part which is here the thickest portion of the bone. Its anterior surface is convex and rough. Its posterior surface presents two lateral articular facets, separated by a crest; this surface is in contact with the trochlea of the femur, and, as it is the internal lip of the latter which is the more developed, it results therefrom that the internal articular surface of the knee-cap is larger than the external.
The knee-cap contributes to the formation of the region of the posterior limb which is called the stifle.
The tibia is large in its upper portion; in its inferior part it is flattened from before backwards. The posterior surface of the shaft presents an oblique line, below which are found vertical rough lines for the insertion of muscles. The external surface is hollowed out in its upper part. The anterior tuberosity of the tibia rises just to the level of the flat articular surface; it is hollowed in its median portion by a vertical groove of elongated form, which receives the ligament that binds the knee-cap to the tibia. The external tuberosity is more prominent than the internal; in it is found a groove for the passage of the anterior tibial muscle.
The inferior extremity, flattened from before backwards, presents a surface which is moulded on the trochlea of the astragalus; the median crest of this surface is thick, and descends lower posteriorly than the tuberosities which are situated on the external and internal aspects of this extremity.
Of the two tuberosities, that which is internal is comparable to the internal malleolus of man, the one on the outer side forms a sort of external malleolus; but this latter here belongs to the tibia, and not to the fibula.
The fibula, in fact, does not reach the inferior extremity of the tibia; it is a poorly developed bone, elongated and terminating inferiorly in a point, at the middle of the shaft of the tibia or at its lower third. Its superior extremity, which is slightly expanded, articulates with the tuberosity which occupies the outer aspect of the corresponding extremity of the tibia.