apidly got rid of by rest and
blistering. If the patient is unable to lie up, massage should be
systematically employed, and a firm elastic bandage worn. A patient
who has once had a severe sprain of the knee, or who has developed the
condition of "footballer's knee," must give up violent forms of
exercise which expose him to further injuries, otherwise the condition
is liable to be aggravated and to result in permanent impairment of
the stability of the joint.

INJURIES OF THE PATELLA

#Fracture of the patella# is a comparatively common injury in adult
males. Most frequently it is due to _muscular action_ the patella
being snapped across the lower end of the femur by a sudden and
forcible contraction of the quadriceps extensor muscle while the limb
is partly flexed--as, for example, in the attempt to avoid falling
backward. The bone is then broken as one breaks a stick by bending it
across the knee, and the line of fracture, which is transverse or
slightly oblique, crosses the bone a little below its middle.
Fractures produced in this way are almost never compound.

[Illustration: FIG. 87.--Radiogram of Fracture of Patella.]

The degree of displacement of the fragments depends upon the extent to
which the expansion of the quadriceps tendon is lacerated. As a rule,
it is but slightly torn, so that the separation of the fragments does
not exceed an inch. In other cases it is widely torn, and the
contraction of the quadriceps muscle is then able to separate the
fragments by three or four inches, and sometimes causes tilting of the
upper fragment. The blood effused into the joint tends still further
to increase the separation. As the periosteum is usually torn at a
level lower than the fracture, its free margin hangs as a fringe from
the proximal fragment, and by getting between the broken ends may form
a barrier to osseous union (Macewen).

_Clinical Features._--Immediately the bone breaks, the patient falls,
and he is unable to rise again, as the limb is at once rendered
useless, and in attempting to do so we have known him to fracture the
patella of the other limb. The power of extending the limb is lost,
and the patient is unable to lift his foot off the ground. The
knee-joint is filled with blood and synovia, which usually extend into
the bursa under the quadriceps. The two fragments can be detected,
separated by an interval which admits of the finger being placed
between them, and which is increased on flexin