48 
bursa behind its ligament. It has been said 
above that besides its ginglymoid motion, the 
knee-joint has a slight arthrodial motion in the 
bent position: this is strictly a rotation of the 
tibia on its axis, and the effect is to point the 
toes more or less to the outer side, rotation in- 
wardly to any great extent being prevented by 
the crucial ligaments. During this movement 
of rotation, the inner articulating surface on 
the head of the tibia advances forwards, while 
at the same time the outer one recedes; the 
lateral ligaments allow of this motion, in con- 
sequence of their inferior attachments being a 
good deal below the margin of the joints and 
the crucial ligaments permit the successive, 
though not the simultaneous, advance or re- 
cession of the cavities on the head of the tibia. 
In all positions of the joint the arrangement is 
such that the attempt to thrust forwards the 
whole head of the tibia is resisted by the ante- 
rior crucial ligament, whilst the posterior pre- 
vents it from being driven backward.* Ihe 
* [The following experiments, which may easily 
be tried, illustrate the respective offices of the se- 
veral ligaments. 
If the external fibrous investment of the joint 
be completely removed, taking care that the lateral 
and crucial ligaments shall be free from injury, 
the motions of the joint will be in no degree af- 
fected; but if the opposite experiment be tried, 
and the lateral and crucial ligaments be cut, leav- 
ing the external fibrous investment uninjured, 
excepting a small hole made for getting at the ligu- 
ments, it will be found that the integrity of the 
joint is completely destroyed, the bones are but 
loosely connected to each other, their apposition is 
destroyed, and they move about indifferently in 
every direction. 
Again, if after dissecting off the external fibrous 
investment both crucial ligaments be cut, leaving 
the lateral ligaments as the only bonds of con- 
nection between the two bones, it is found that 
during extension, the fixedness of the joint is un- 
impaired, but if flexion be made gradually, the 
bones becomes less in apposition and more move- 
able, and in the completely bent state of the limb, 
they become quite loosely connected and may rea- 
dily be moved from side to side, and the only limit 
to flexion is from the tibia coming against the 
femur, 
’ If the lateral ligaments be cut, leaving the cru- 
cial uninjured, the bones remain firmly connected 
when the joint is in the state of complete flexion, 
and the crucial ligaments still, as in the natural 
state, oppose any further flexion. In the gradual 
diminution of the flexion, the junction of the bones 
becomes less complete, and when the extension 
has been carried to its full extent, the bones may 
be separated from each other, and admit of lateral 
motion; and if the joint be held‘up so as to allow 
the tibia to hang from it, the foot will become 
everted by its own weight, and the two crucial liga- 
ments, instead of their crossed and oblique position, 
will assume a parallel and vertical direction. These 
experiments are described by Weber, but there are 
few anatomists in this country, for many years back, 
who have not frequently tried them. 
The office of the semilunar cartilages is three- 
fold: 1. filling up the empty space which the arti- 
cular surfaces leave around their point of contact, 
they distribute the pressure over a greater surface ; 
2. they serve to distribute the tension of the liga- 
ments in the movements of the joint more uni- 
formly, and thereby to oppose any jarring of the 
bones against each other; and, thirdly, theydeaden 
the vibrations which in the various movements of 
ABNORMAL CONDITIONS OF THE KNEE-JOINT. a 
- branches, viz.two superior articular, which 
mucous ligament and fatty body of the jo 
change their situation in some degree duri 
its motions and may serve to fill spaces 1 
which would otherwise be left vacant: th 
that they are peculiarly concerned in secreti 
the synovia has been satisfactorily refuted 1 
der “ AnticuLaTiIon.” Z- 
The burse in the neighbourhood of the kn 
joint are numerous and not unimportant, ff 
the circumstance that some of them often 
into the joint itself. In the layers of fas 
anterior to the patella, one or more exist, 1 
perfectly formed and very liable to inflam 
suppurate. The situations in which the m 
pe ect specimens are found are as folle 
hind the ligament of the patella; ' 
the cruralis and fore-part of the os femo 
beneath the internal lateral ligament; at | 
insertion of the semitendinosus, gracilis, 2 
sartorius ; underneath each head of the gem 
oe ; and around the tendons of the s a an 
ranosus and liteus respectively ; 
named bursa PL ps ares on et distan 
between the popliteus and the tibia, and 
often communicates below with the supe 
tibio-fibular articulation, as well as with 
knee-joint above. This joint is supplied wi 
blood from the popliteal artery by five differ 
round the lower part of the os femoris; one mi 
dle articular which passes through the posteri¢ 
ligament to the central parts of the joint; am 
two inferior articular, which take their cour 
round the head of the tibia, and anastor 
freely with each other, and with the two upp 
the returning veins go to the popliteal. ss 
The comparative anatomy of the knee-joit 
gives for the most part the same essential. struc 
ture as we have described in man, ‘though va 
riously modified. ; 
In most animals, when in a standing pos 
ture, the knee maintains habitually a state 
flexion, and this arrangement conduces muc 
to fleetness and agility of motion. In the ele 
phant, however, the bones of the hind leg fort 
an upright pillar of support, and the knee is @ 
tended as in the human subject. The elephai 
also resembles man in the circumstance of th 
knee being brought to the ground in kneeling 
whereas, in most genera, the true knee is plac 
much nearer to the body of the animal. 
(Alfred Higginson.) 
KNEE-JOINT, asnormaL CONDITION 
or.—The abnormal conditions of the kne 
joint may be arranged under those which resu 
from disease and accident. The deviations 0 
casionally met with as the consequence of cor 
genital malformation are fortunately rare. _ 
DisEase.—The abnormal appearances in t 
knee-joint resulting from disease are those whi 
spring from some specific irritation, such 4 
struma, gout, rheumatism, syphilis, or malig 
nant disease, or from direct violence. Most 0 
these irritations affect all the structures of the 
the limbs, especially in standing, walking, or un- 
ning, are propagated along the bones,—VideWebe 
Mechanik, &c. p. 193. Ep.] a 
