NORMAL ANATOMY OF THE KNEE-JOINT. 
ment of the lateral ligaments ; below which, on 
the outer condyle, there is a pit for the origin 
of the popliteus tendon, and a fossa leading 
“upwards and backwards from it which lodges 
the tendon when the joint is fully flexed. In 
the lateral aspect of the bone we best see the 
— curvature of the articulating surface. 
_ In two adult, but rather small, specimens before 
me the inferior part of the outer condyle is a 
Segment of a circle of fourteen lines radius, 
while the radius of the posterior portion is only 
_ Seven lines; similar measurements of the curves 
“of the internal condyle give radii of six and 
“twelve lines respectively: the centre of the 
‘smaller circle coincides precisely with the point 
of attachment of the lateral ligament on each 
side, and the advantages of this arrangement 
will appear when we come to consider the 
functions of the joint. The smooth articulating 
Surface of the trochlea and condyles is, in the 
 Tecent state, covered with cartilage. Above 
_ this surface and in the fossa between the con- 
dyles are numerous foramina for the transmis- 
sion of the nutrient vessels of the bone, the 
internal structure of which is here made up of 
Minute cancelli. The lower extremity of the 
08 femoris is cartilaginous at birth, becomes 
ossified from a separate centre, and long conti- 
_ hues to form an epiphysis ; but it is ultimately 
_ Joined to the shaft by perfect bony union. 
The thigh-bone exposes the largest extent of 
surface in the knee-joint; that of the tibia is 
_ the next in size. Its superior extremity is ex- 
panded into the same kind of cancellated struc- 
ture as the os femoris possesses at its lower 
_ part; and the width from side to side equals 
that of the condyles, which rest upon its upper 
Surface. That surface is nearly horizontal, in 
the erect position of the body ; ‘it is irregularly 
_ oval, the long axis passing from side to side, 
_ and is marked in the centre by a rough promi- 
_ hence or spine, in front of which is a depression, 
_ and at the back part a notch. On each side of 
_ these inequalities there is a smooth articular 
surface; the inner one the larger, especially 
from before backwards, and slightly concave ; 
while the outer one is flat round the margin 
_ and raised at the inner side by the base of the 
Spine. Viewing the bone in its anterior aspect 
we observe that below the articular surface it 
_ slopes downwards and forwards to the tubercle 
| which stands out at the upper part of the shin 
_ Or crest of the tibia; this tubercle gives insertion 
_ at its lower part to the strong ligament of the 
_ patella, a bursa being interposed between that 
ligament and its upper smooth portion. Nu- 
_ merous foramina are to be observed round the 
head of the bone for the purposes of its nutri- 
tion. Below the tubercle a section of the tibia 
shows it much reduced in size and somewhat 
_ triangular in shape; the outer side forming, in 
conjunction with the fibula, a large fossa for the 
tibialis anticus and other muscles; and the 
inner, facing also anteriorly, being a portion of 
that surface of bone which is covered only by 
skin and periosteum ; except at its upper part, 
where three flat tendons pass upon it to be 
inserted by the side of the tubercle in the follow- 
ing order; that of the semitendinosus lowest, 
45 
the gracilis next above, and the sartorius the 
highest up and most anteriorly. The posterior 
surface of the tibia at the supposed place of 
section has advanced considerably forwards, so 
as to leave a hollow for the popliteus muscle 
which lies obliquely on this part of the bone. 
A few lines below the great articulating surface 
on the head of the tibia there are two things to 
be noticed on its posterior aspect; at the outer 
side a small articular surface for the head of the 
fibula, and at the inner side a shallow pit 
where the tendon of the semimembranosus is 
inserted. } 
The patella is a flat disk of bone placed in 
front of the knee-joint; it equals in width the 
trochlea of the os femoris to which it is applied, 
the posterior surface being for that purpose 
covered with cartilage and divided into two 
slight cavities by a prominent vertical line ; the 
articular surface is oval from side to side and 
does not reach to the lower edge of the bone. 
Anteriorly, the patella is convex, and its hori- 
zontal slightly exceeds its vertical measure- 
ment, particularly in the female ; into its upper 
edge are inserted the united tendons of the 
rectus, cruralis, and vasti muscles; into its 
lower edge the strong ligamentum patelle 
which joins it to the tubercle of the tibia; it is 
covered only by skin, fascia, and some ten- 
dinous fibres, to which latter may be attributed 
the appearance of vertical strie observable on 
the bone. 
(b.) Cartilages, ligaments, §c.—-The whole 
of the bony surfaces which come into contact 
with each other or with the interarticular carti- 
lages during the movements of the knee-joint 
are covered with “ cartilages of incrustation ” 
(see ARTICULATION); and the extent of these 
on the condyles and trochlea of the os femoris, 
on the head of the tibia and the posterior sur- 
face of the patella, is well marked even in the 
dry bones by their smooth and compact ap- 
pearance and the total absence of foramina on 
the parts so covered. Besides these pure car- 
tilages there are two fibro-cartilages of a semi- 
lunar form lying upon the head of the tibia, 
which serve to deepen the articulating surfaces 
for the reception of the condyles. These semi- 
Innar cartilages, (cartilagines falcata, s. lu- 
nate) as they are named, are thickest at their 
convex edges which are attached rather loosely 
to the circumference of the head of the tibia ; 
the concave edges are thin and sharp, and lie 
unattached between the condyles and the tibia. 
The two semilunar cartilages differ slightly 
from each other in the two following points ; 
the inner one is falciform, decreasing in breadth 
from behind forwards; the greatest width being 
“at the inner and back part, five-eighths of an 
inch, whilst in front it is hardly more than one 
quarter of an inch; the anterior and posterior 
cornua are separated to the distance of an inch, 
whilst those of the outer semilunar cartilage 
approach to within three-eighths of an inch of 
each other; and, besides that the ring is thus 
more nearly completed, the breadth of the outer 
one is more uniform, being about three-eighths 
of an inch throughout the greater part. The 
thickness of either of them barely exceeds one- 
