Proliferative 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 long life, but not with any active occupation, hence those of the hospital class who suffer from it tend to accumulate in workhouse infirmaries.

Hydrops is most marked in the knee, and may affect also the adjacent bursae.  As the joint becomes distended with fluid, the ligaments are stretched, the limb becomes weak and unstable, and the patient complains of a feeling of weight, of insecurity, and of tiredness.  Pain is occasional and evanescent, and is usually the result of some extra exertion, or exposure to cold and wet.  This form of the disease is extremely chronic, and may last for an indefinite number of years.  It is to be diagnosed from the other forms of hydrops already considered—­the purely traumatic, the pyogenic, gonorrhoeal, tuberculous, and syphilitic—­and from that associated with Charcot’s disease.