changes in the synovial membrane are attended with
increased vascularity and thickening of the membrane and an enlargement
of its villi and fringes. When the fatty fringes are developed to an
exaggerated degree, the condition is described as an _arborescent
lipoma_ (Fig. 159). Individual fringes may attain the size of a hazel
nut, and the fibro-fatty tissue of which they are composed may be
converted into cartilage and bone; such a body may remain attached by a
narrow pedicle or stalk, or this may be torn across and the body becomes
loose and, unless confined in a recess of the joint, it wanders about
and may become impacted between the articular surfaces. These changes in
the synovial membrane are often associated with an abundant exudate or
hydrops. These degenerative and hypertrophic changes, while usually
attended with marked restriction of movement and sometimes by "locking"
of the joint, practically never result in ankylosis.

The _ankylosing type_ of chronic arthritis is fortunately much rarer
than those described above, and is chiefly met with in the joints of the
fingers and toes and in those of the vertebral column. The synovial
membrane proliferates, grows over the cartilage, and replaces it, and
when two such articular surfaces are in contact they tend to adhere,
thus obliterating the joint, cavity, and resulting in fibrous or bony
ankylosis. The changes progress slowly and, before they result in
ankylosis, various sub-luxations and dislocations may occur with
distortion and deformity which, in the case of the fingers, is extremely
disabling and unsightly (Fig. 160).

_Clinical Features._--It is usually observed that in patients who are
still young the tendency is for the disease to advance with considerable
rapidity, so that in the course of months it may cause crippling of
several joints. The course of the disease as met with in persons past
middle life is more chronic; it begins insidiously, and many years may
pass before there is pronounced disability. The earliest symptom is
stiffness, especially in the morning after rest, which passes off
temporarily with use of the limb. As time goes on, the range of movement
becomes restricted, and crackings occur. This stage of the disease may
be prolonged indefinitely; if it progresses, stiffness becomes more
pronounced, certain movements are lost, others develop in abnormal
directions, and deformed attitudes add to the disablement. The disease
is compatible with