TUMOURS OF THE KNEE IN CATTLE. 
547 
The cutaneous form consists either in excessive thickening of the skin 
and subcutis covering the front of the knee, not infrequently associated 
with active increase in the epidermis covering it (fig. 201), by which a 
hard swelling, often as large as a man’s head, results, or in the develop¬ 
ment in the subcutis of cavities filled with serous fluid, which often 
contains lymph flocculi. Hence the condition is sometimes regarded 
as “ capped knee ” and is compared with the retention cysts. The 
descriptions given indicate that in many cases cysts form in the cutis 
and subcutis at the same time that the epidermis undergoes active pro¬ 
liferation. Johne describes this condition as “ dermoid cyst, with diffuse 
keratosis.” 
The synovial form consists in a tendovaginitis chronica serosa or 
fibrosa, which sometimes affects the tendon sheaths of the extensor 
pedis, but more frequently the sheath of the extensor metacarpi magnus. 
The swelling is sometimes chiefly formed by the sheaths of the tendons 
distended with serum (tendovaginitis chronica serosa), sometimes by the 
greatly thickened connective tissue of the sheath and its surroundings 
(tendovaginitis chronica fibrosa). This disease of the tendon sheaths 
has often been found due to tuberculosis. 
A soft and hard form can be distinguished. The tendon sheaths are 
often greatly distended; in one Gurlt found 17 lbs, of fluid. Small 
papillae form on the inner surface of the sheaths, and when rubbed off 
appear like grains of rice ; this condition is termed hygroma proliferum. 
Pus formation may also occur. 
The articular form presents a true tumor albus, that is, progressive 
increase and induration in the peri- and para- articular connective tissue, 
and is always associated with exostosis formation on the bones of the 
knee, fore arm, and metacarpus. The swellings are of variable hard¬ 
ness, and result from chronic inflammation of the knee-joint. Ossification 
in the new connective tissue increases the hardness of the swelling. 
Causes. The chief causes are injuries sustained in lying down and 
rising in badly-paved stalls and on insufficient bedding. The repeated 
bruising may cause extravasation of blood in or under the skin, or into 
the sheaths of the tendons, and proliferation of connective tissue. That 
bleeding often occurs is shown both by the presence of clots in the 
serous fluid, and by the pigmented condition of the newly-formed con¬ 
nective tissue. A single severe bruise from falling on uneven, hard 
ground, as occurs in working-oxen, may produce the disease. Chronic 
processes, like tuberculosis, invading the carpal joint, may also induce 
such tumours, but the nature of the cases hitherto reported is seldom 
fully explained. 
Symptoms and course. The chief symptom consists of swelling of 
the front of the knee, which sometimes increases rapidly, sometimes 
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