14. The phenomena which announce the presence of foreign bodies in
the joint of the knee, are sometimes clothed in a character of such
evidence, that they cannot be mistaken; at other times, the nature of
the disease eludes the most accurate researches: the cause of this
variety may be easily perceived.
As the joint presents different depressions and eminences, and as the
bodies, being usually loose and detached, may travel through its whole
extent, they produce different effects, according to the particular
situations which they occupy. If lodged in a depression, they are
not compressed, and cannot, of course, give rise to any troublesome
affection. If they bear on an eminence, such as the condyls, or the
posterior part of the rotula, they are forcibly compressed, and must
derange, in some measure, the functions of the joint. Hence the precise
nature of the affection cannot be at all times derived from the state
of the symptoms.
15. Sometimes the patient can stand and walk with perfect freedom
and ease, while, at other times, a sudden pain seizing him, obliges
him to sit down, or even causes him to fall, if there be nothing at
hand to support him. This pain subsists for a longer or shorter time.
One motion produces it, and sometimes another, made in an opposite
direction, removes it. But in common it is of some continuance, and
then the patient is obliged to keep his bed.
16. If the state of the joint be examined, it will be found more or
less swollen, when the pain is very acute. When the pain ceases,
the swelling in part disappears. It is never sufficient to prevent
the fingers, when drawn along the external surface of the joint,
from discovering the presence of the foreign body, when it forms a
protuberance under the integuments. It is then found sometimes above
the rotula, by the side of the tendon of the extensor muscles, and that
is the place where it usually produces least pain; at other times,
it is lower down, in front of the condyls, and by the side of the
rotula. It is occasionally found immediately behind the tendon of the
extensor muscles; in this case so acute is the pain, that the patient
is generally unable to stand. But it is when it is situated behind the
rotula, near to the projecting ridge which runs across its posterior
surface, that it gives rise to the most serious affections.
17. The body passes from one place to another, on the least motion,
and sometimes, as Bell observes, the patient, on changing his position
during sleep, is awakened by severe pain, in consequence of the foreign
body being moved by this change. It happens, in certain cases, that it
disappears, and lies concealed for some time, in the back part of the
joint. During this period the joint performs all its functions with
freedom and ease. Desault made this remark, in the case of a captain of
dragoons, from whom, for the first time in his practice, he extracted
one of these bodies, and who, for six months previously, had been able
to perform all the motions of the joint freely, without pain. This
person, experiencing no uneasiness, considered himself perfectly cured,
when the body suddenly reappeared, in consequence of a hasty extension
of the leg.
18. If the body, when projecting under the integuments, be gently
compressed, it yields to the pressure, changes its situation, and,
according to the impression it has received, moves either to the
internal or the external side of the joint, or reciprocally from one
side to the other, passing also behind the rotula, behind the inferior
ligament, or sometimes behind the tendon of the extensor muscles. In
these alternate displacements, it may in some cases be turned round,
in such a manner that its anterior surface will take the place of its
posterior one, and then resume its primitive situation. Desault met
with an instance, in which the patient himself was in the habit of
turning the body round in this manner.
19. Bell, in conformity to the distinction of articular concretions
into cellular and solid, attributes to each division its peculiar
signs. In the first case, the pains, being rather obtuse than sharp,
are constant; in the second, they are extremely acute, but disappear
and return at intervals. Supposing the division to be a real one, cases
of the last description certainly occur much more frequently than those
of the first.
§ V.