The disease spreads throughout the capsule and synovial membrane, which becomes diffusely thickened and infiltrated with granulation tissue which eats into and replaces the articular cartilage.  Clinically, the condition resembles tuberculous disease of the synovial membrane, for which it is probably frequently mistaken, but in the syphilitic affection the swelling is nodular and uneven, and the subjective symptoms are slight, mobility is little impaired, and yet the deformity is considerable.

Syphilitic osteo-arthritis results from a gumma in the periosteum or marrow of one of the adjacent bones.  There is gradual enlargement of one of the bones, the patient complains of pains, which are worst at night.  The disease may extend to the synovial membrane and be attended with effusion into the joint, or it may erupt on the periosteal surface and invade the skin, forming one or more sinuses.  The further progress is complicated by the occurrence of pyogenic infection leading to necrosis of bone, in the knee-joint, for example, the patella or one of the condyles of the femur or tibia, may furnish a sequestrum.  In such cases, anti-syphilitic treatment must be supplemented by operation for the removal of the diseased tissues.  In the knee, excision is rarely necessary; but in the elbow it may be called for to obtain a movable joint.

In #inherited syphilis# the earliest joint affections are those in which there is an effusion into the joint, especially the knee or elbow; and in exceptional cases pyogenic infection may be superadded, and pus form in the joint.

In older children, a gummatous synovitis is met with of which the most striking features are:  its insidious development, its chronic course, symmetrical distribution, freedom from pain, the free mobility of the joint, its tendency to relapse, and its association with other syphilitic stigmata, especially in the eyes.  The knees are the joints most frequently affected, and the condition usually yields readily to anti-syphilitic treatment without impairment of function.

JOINT DISEASES ACCOMPANYING CERTAIN CONSTITUTIONAL CONDITIONS

#Gout.#—­Arthritis Urica.—­One of the manifestations of gout is that certain joints are liable to attacks of inflammation associated with the deposit of a chalk-like material composed of sodium biurate, chiefly in the matrix of the articular cartilage, it may be in streaks or patches towards the central area of the joint, or throughout the entire extent of the cartilage, which appears as if it had been painted over with plaster of Paris.  As a result of this uratic infiltration, the cartilage loses its vitality and crumbles away, leading to the formation of what are known as gouty ulcers, and these may extend through the cartilage and invade the bone.  The deposit of urates in the synovial membrane is attended with effusion into the joint and the formation of adhesions, while in the ligaments and peri-articular structures it leads to the formation of scar tissue.  The metatarso-phalangeal joint of the great toe, on one or on both sides, is that most frequently affected.  The disease is met with in men after middle life, and while common enough in England and Ireland, is almost unknown in hospital practice in Scotland.