224 OSTEOLOGY. 
attachment of the vastus internus being more extensive than that of the vastus 
externus. The anterior surface of the bone, slightly convex in both diameters, has 
a fibrous appearance, due to its longitudinal striation, and is pierced here and there 
by the openings of vascular canals. The posterior or femoral articular surface is 
divided into two unequal parts (of which the external is the wider) by a vertical 
elevation which glides in the furrow of the trochlear surface of the femur, and in 
extreme flexion passes to occupy the intercondylic notch. The outer of the two 
femoral surfaces is slightly concave in both its diameters; the inner, though 
slightly concave from above downwards, is usually plane, or somewhat convex trans- 
versely. Occasionally, in the macerated bone, indications of a third vertical area 
are to be noted along the inner edge of the internal aspect. This defines the 
part of the articular surface which rests on the border of the internal condyle in 
extreme flexion. 
3elow the femoral articular area the deep surface of the apex is rough and 
irregular; the greater part of this is covered by synovial membrane, the liga- 
mentum patelle being attached to its summit and margins, reaching some little 
distance round the borders on to the anterior aspect of this part of the bone. 
Architecture.—The bone consists of a thick dense layer anteriorly, which thins towards the 
edges on either side and below ; above, it corresponds to the area of insertion of the quadriceps. 
The femoral articular surface is composed of a layer of compact bone, thickest in correspondence 
with the vertical elevation. Sandwiched between these two layers is a varying thickness of 
spongy tissue of fairly close grain, the striation of which on cross section runs in parallel lines 
from back to front; on vertical section the tissue appears to be arranged in lines passing radially 
from the deep surface of the femoral area to the more extensive anterior dense plate. 
Variations. —Cases of congenital absence of the patella have been recorded. 
Ossification.—The patella is laid down in cartilage about the third month of foetal 
life. At birth it is cartilaginous, and the tendon of the quadriceps is continuous with 
the ligamentum patellee over its anterior surface, and can easily be dissected off. 
About the third year an ossific centre appears in it and spreads more particularly over 
its deeper surface. Ossification is usually completed by the age of puberty. 
THE TIBIA. 
The tibia is the inner bone of the leg. It is much stouter and stronger than its 
neighbour the fibula, with which it is united above and below. By its superior 
expanded extremity it supports the condyles of the femur, while inferiorly it shares 
in the formation of the ankle-joint, articulating with the upper surface and inner 
side of the astragalus. 
The superior extremity comprises the inner and outer tuberosities, the spine, 
and the tubercle. Each tuberosity is provided on its upper aspect with an articular 
surface (facies articularis superior), which supports the corresponding femoral 
condyle, as well as the interposed semilunar cartilage. Of these two condyle 
surfaces, the inner is 
Sa Jh the larger; of oval 
ofant. oxtremity of) Shape, its long axis 
external semilunar cart. is placed antero - pos - 
tm, teriorly. Slightly 
if ; concave from before 
Le backwards and from 
side to side, its cir- 
EXTERNAL : : 
TUBEROSITY cumference rises in 
the form of a sharp 
and well-defined edge. 
WW Surface for attach. of r 
post. extremity of The outer condylic 
Surface for attachment of anterior TUBERCLE 
extremity of internal semilunar cartilage 
Anterior crucial ligament 
SPINE fos 
INTERNAL 
TUBEROSITY 
SYNOVIAL CURVED 
SURFACE ea ' PopLITEAL ey semilunar surface is smaller and 
Surface for attach. of post. extrem. NOTCH ana ; F 3 
of internal semilunar cartilage Post. crucial ligament rounder. §S ligh tly 
concave from side to 
side, and gently con- 
vex from before backwards, its circumference is well defined in front, but is 
rounded off behind, thus markedly increasing the convexity of its posterior part. 
Fic. 167.—UPpreR SURFACE OF SUPERIOR EXTREMITY OF RIGHT TIBIA. 
