14 
_____ Abscess may, however, form in the interior 
__ f the heads of the tibia or lower extremity of 
le femur without being preceded by the death 
f any portion of the bone, as is proved by a 
ecimen in the museum of the Richmond 
ospital. A child, aged about twelve, had 
mg suffered from chronic disease of the upper 
rtion of the tibia. A chronic symptomatic 
scess pointed and opened spontaneously in 
le popliteal space, and here a fistulous open- 
ig remained discharging a quantity of thin 
pious pus. While under treatment for this 
ic disease, a sudden attack of acute ar- 
is set in, which threatened the patient’s 
_and amputation was immediately per- 
d. Upon examination of the knee-joint 
1 of the interior of the bones, which were 
posed by a vertical section made from before 
ards, an abscess was discovered in the 
ntre of the head of the tibia, capable of con- 
ining a walnut. This communicated with 
B popliteal abscess, which had long had a 
tulous opening in the ham ; but the abscess 
he interior of the tibia was now found to 
another opening into the cavity of the 
joint, which had all the appearance of 
g been quite recent. The matter of the 
ss of the tibia having suddenly made 
its way into the cavity of the knee-joint was the 
immediate exciting cause of the acute arthritis 
au, evidences of which were seen in a layer 
lymph which invested the synovial mem- 
we and the cartilages. The patient ulti- 
mately recovered. 
_ When the chronic form of necrosis affects 
he tibia and the epiphysis is included in the 
lisease, the knee-jojnt sometimes remains but 
altered, but in other cases remarkable 
S in its form take place. The leg is 
imes fully extended, and is even in ad- 
ce of the natural line, but it is more gene- 
ally flexed on the femur, and the tibia is at 
same time somewhat curved into the form 
fan arch, the concavity looking forwards. We 
have frequently known displacement of the su- 
erior head of the tibia, where it enters into the 
ormation of the knee-joint, to take place back- 
bards towards the popliteal space. This dis- 
lacement is usually incomplete. We have 
xamined many living examples of this defor- 
hity, and have had a few opportunities of inves- 
gating the anatomical changes the joint has 
een subjected to. 
Many circumstances tend to influence the 
rection in which the luxation may take place. 
he position in which the limb is preserved 
the attack ofinflammation of the tibia is 
f the most influential. As the limb is 
ly flexed during the first stage of the 
e, the partial luxation backwards will be 
ne most likely to occur. In these cases, 
ther the femur or tibia close to the knee be 
@ seat of the necrosis, more or less of effusion 
8 place into the synovial sac of the knee- 
joint; all the ligaments, of the joint become 
softened and relaxed; and the action of the 
Hamstring muscles overcomes the resistance of 
any remaining structures, and the tibia is dis- 
tocated partially backwards. 
VOL, 11k 
: 
4 ABNORMAL CONDITIONS OF THE KNEE-JOINT. 
65 
Mr. West, surgeon to the Longford Infir- 
mary, sent to the writer of this article the leg 
and knee-joint of a man who had long con- 
tended against the consequences of a chronic 
necrosis of the tibia. There were from time to 
time exfoliations of bone, and a continual dis- 
charge of a thin sanious matter which so re- 
duced the strength of the patient as to render 
amputation necessary. <A cast of the limb, taken 
by Mr. Smith, and the bone are preserved in 
the museum of the Richmond Hospital, (figs. 
4 and 5,) from whichit will be observed that the 
fi 
\ 
\ 
Displacement of the tibia backwards from necrosis. 
displacement of the head of the tibia was par- 
tially backwards. This bone was drawn also 
somewhat upwards, passing inferiorly so far 
round the condyles of the femur that the arti- 
cular surfaces were almost abandoned. This 
is the simplest form of displacement of the 
tibia at the knee-joint from disease which we 
have noticed as the result of a chronic process 
of necrosis. We have seen some instances of 
necrosis in which the whole leg and foot were 
greatly rotated outwards on the femur, so that 
the innet ankle was placed directly forwards, 
and the outer malleolus directly backwards. In 
these cases the patella is completely dislocated 
on the outer condyle of the femur (fig. 6), be- 
cause the tubercle of the tibia, in its movement of 
rotation outwards, carries with it the ligamentum 
F 
