#Haemophilic# or #Bleeder’s Joint#.—­This is a rare but characteristic affection met with chiefly in the knee-joint of boys who are the subjects of haemophilia.  After some trivial injury, or even without apparent cause, a haemorrhage takes place into the joint.  The joint is tensely swollen, cannot be completely extended, and is so painful that the patient is obliged to lie up.  The temperature is often raised (101 to 102 F.), especially if there are also haemorrhages elsewhere.  The blood in the joint is slowly re-absorbed, and by the end of a fortnight or so, the symptoms completely disappear.  As a rule these attacks are repeated; the pain attending them diminishes, but the joint becomes the seat of permanent changes:  the synovial membrane is thickened, abnormally vascular, and coloured brown from the deposit of blood pigment; on its surface, and in parts of the articular cartilage, there is a deposit of rust-coloured fibrin; there may be extensive adhesions, and in some cases changes occur like those observed in arthritis deformans with erosion and ulceration of the cartilage and a form of dry caries of the articular surfaces, which may terminate in ankylosis.

As the swelling of the joint is associated with wasting of the muscles, with stiffness, and with flexion, the condition closely resembles tuberculous disease of the synovial membrane.  From errors in diagnosis such joints have been operated upon, with disastrous results due to haemorrhage.

The treatment of a recent haemorrhage consists in securing absolute rest and applying elastic compression.  The introduction of blood-serum (10-15 c.c.) into a vein may assist in arresting the haemorrhage; anti-diphtheritic serum is that most readily obtainable.

After an interval, measures should be adopted to promote the absorption of blood and to prevent stiffness and flexion; these include massage, movements, and extension with weight and pulley.

JOINT DISEASES ASSOCIATED WITH LESIONS OF THE NERVOUS SYSTEM:  NEURO-ARTHROPATHIES

In Lesions of Peripheral Nerves.—­In the hand, and more rarely in the foot, when one or other of the main nerve-trunks has been divided or compressed, the joints may become swollen and painful and afterwards become stiff and deformed.  Bony ankylosis has been observed.

In Affections of the Spinal Medulla.—­In myelitis, progressive muscular atrophy, poliomyelitis, insular sclerosis, and in traumatic lesions, joint affections are occasionally met with.

The occurrence of joint lesions in locomotor ataxia (tabes dorsalis) was first described by Charcot in 1868—­hence the term “Charcot’s disease” applied to them.  Although they usually develop in the ataxic stage, one or more years after the initial spinal symptoms, they may appear before there is any evidence of tabes.  The onset is frequently determined by some injury.  The joints of the lower extremity are most commonly affected, and the disease is bilateral in a considerable proportion of cases—­both knees or both hips, for instance, being implicated.