[Illustration: FIG. 163.--Charcot's Disease of Left Knee. The joint is
distended with fluid and the whole limb is oedematous.]
The rapidity of the destructive changes in certain cases of tabes, and
the entire absence of joint lesions in others, would favour the view
that special parts of the spinal medulla must be implicated in the
former group.
In _syringomyelia_, joint affections (gliomatous arthropathies) are more
frequent than in tabes, and they usually involve the upper extremity in
correspondence with the seat of the spinal lesion, which usually affects
the lower cervical and upper thoracic segments. Except that the joint
disease is seldom symmetrical, it closely resembles the arthropathy of
tabes. The completeness of the analgesia of the articular structures
and of the overlying soft parts is illustrated by the fact that in one
case the patient himself was in the habit of letting out the fluid from
his elbow with the aid of a pair of scissors, and that in another the
joint was painlessly excised without an anaesthetic.
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