lly a swelling of the joint and its vicinity.
There is no redness or heat and no pain on movement. The peri-articular
swelling, unlike ordinary oedema, scarcely pits even on firm pressure.

[Illustration: FIG. 162.--Bones of Knee-joint in advanced stage of
Charcot's Disease. The medial part of the head of the tibia has
disappeared.

(Anatomical Museum, University of Edinburgh).]

In mild cases this condition of affairs may persist for months; in
severe cases destructive changes ensue with remarkable rapidity. The
joint becomes enormously swollen, loses its normal contour, and the ends
of the bones become irregularly deformed (Fig. 162). Sometimes, and
especially in the knee, the clinical features are those of an enormous
hydrops with fibrinous and other loose bodies and hypertrophied
fringes--and great oedema of the peri-articular tissues (Fig. 163). The
joint is wobbly or flail-like from stretching and destruction of the
controlling ligaments, and is devoid of sensation. In other cases,
wearing down and total disappearance of the ends of the bones is the
prominent feature, attended with flail-like movements and with coarse
grating. Dislocation is observed chiefly at the hip, and is rather a
gross displacement with unnatural mobility than a typical dislocation,
and it is usually possible to move the bones freely upon one another and
to reduce the displacement. A striking feature is the extensive
formation of new bone in the capsular ligament and surrounding muscles.
The enormous swelling and its rapid development may suggest the growth
of a malignant tumour. The most useful factor in diagnosis is the entire
absence of pain, of tenderness, and of common sensibility. The freedom
with which a tabetic patient will allow his disorganised joint to be
handled requires to be seen to be appreciated.

[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 jo