752 THE BOXES AXD JOINTS. 



ative changes of surrounding parts. According to the prominence of 

 one or other of these secondary alterations, several forms of tuberculous 

 arthritis may be distinguished. If there is an excessive growth of gran- 

 ulation tissue without much suppuration, this constitutes a fungous form. 

 Sometimes there is extensive suppuration, so that the cavity of the joint 

 may be filled with pus, which may be discharged through openings in 

 the skin ; or there may be more or less extensive formation of abscesses, 

 or infiltration of the soft parts about the joint with pus. In other cases 

 there is disintegration of the new-formed tuberculous tissue and of the 

 tissues of the joint ulcerative form. The cartilage basement substance 

 may become split into fragments and the cells degenerate, and thus deep 

 and destructive ulcers of the cartilage may be formed. Or the new tissue 

 may work its way through the cartilage into the bone beneath, by absorp- 

 tion of the basement substance of the cartilage, with or without prolifer- 

 ation of its cells. Caries and necrosis of the underlying bone may lead 

 to extensive destruction. Hand-iu-haud with these alterations subperi- 

 osteal new formation of bone may occur, or sclerosis of the adjacent 

 bone tissue. There may also be a great increase of fibrous tissue about 

 the joint. 



This disease is most common in children and young persons. The 

 so-called scrofulous diathesis is said to foster it, but local injuries are 

 frequently the predisposing factors. It is most common in the large 

 joints. It may occur in connection with tuberculous inflammation in other 

 parts of the body, but it is frequently quite local, and may remain so 

 for a very long time or permanently, since general infection from tuber- 

 culous arthritis is comparatively infrequent. 



The process is usually slow, and may end in death. If recovery takes 

 place before the cartilages and bones are involved, the joint is preserved ; 

 but it may be stiffened, or even immovable, from the contraction of the 

 new fibrous tissue around it. If the cartilages and bones are diseased 

 the joint is destroyed, and either bony or fibrous aukylosis results. 

 Sometimes, from the change in the articulating surfaces and the contrac- 

 tion of the muscles and the new fibrous tissue, partial or complete dis- 

 locations are produced. 



Occasionally rniliary tubercles occur in the syuovial membranes in 

 cases of general miliary tuberculosis, with but little accompanying simple 

 inflammatory change. 



TUMORS. 



Secondary tumors of the joints as a result of local extension from the 

 adjacent parts are not uncommon, and the tumors may be of various 

 kinds. Primary tumors of the joints, on the contrary, are not very 

 common. 



Lipoma. A new growth of fat tissue may begin in the other portions 

 of the synovial membrane, push this inward, and project into the joint 

 in a mass of tufts liporna arborescens. 



