nisci. On account of the
swelling, which obscures the outline of the part, the differential
diagnosis is often difficult, but as the swelling goes down under
massage it becomes easier. Chief reliance is to be placed upon the
bony points retaining their normal relationships, and upon the fact
that the points of maximum tenderness are over the attachments of one
or other of the collateral ligaments. As the tibial collateral
ligament suffers most frequently, the most tender spot is usually over
its attachment to the medial aspect of the head of the tibia--less
frequently over the medial condyle of the femur.

Unless efficiently treated, a sprain of the knee is liable to result
in weakness and instability of the joint from stretching of the
ligaments, and this is often associated with effusion of fluid in the
synovial cavity (_traumatic hydrops_). This is more likely to occur if
the joint is repeatedly subjected to slight degrees of violence, such
as are liable to occur in football or other athletic exercises--hence
the name "footballer's knee" sometimes applied to the condition.

A further cause of disability, following upon sprains of the knee, is
_wasting of the quadriceps muscle_. The stability of the joint,
whenever the position of full extension has been departed from, is
largely dependent upon its capacity of controlling the amount of
flexion, notably in descending a stair or in walking on uneven ground,
hence it is that with a wasted quadriceps there is increasing
liability to a repetition of the sprain. With each repetition of the
sprain, there is an addition to the fluid in the joint, stretching of
ligaments, and further wasting of the quadriceps. A form of vicious
circle is established in which there is at the same time increased
liability to sprain and diminished capacity of recovering from it.
Even after the repair of the damaged ligament or the removal of the
mobile or torn meniscus, wasting of the quadriceps remains a source of
weakness and disability and calls for treatment by massage and
electricity.

_Treatment._--In recent and severe cases the patient must be confined
to bed, and firm pressure applied over the joint by means of cotton
wool and a bandage. This may be removed once or twice a day to admit
of the joint being douched, and at the same time it should be massaged
and moved to promote absorption of the effusion and prevent the
formation of adhesions.

Chronic effusion into the joint is most r