THE BONES AND JOINTS. 751 



able deformity. Not iiif requeiitly fibrous and bony ankyloses are formed 

 between the ends of the bones. 



Arthritis deformans. This name has been applied to a variety of 

 chronic inflammation of the joints which, combined with degeneration of 

 parts of the joint and the new formation of bone, may result in marked 

 deformities of the part. 



It usually occurs in elderly persons and is apt to involve several 

 joints, most frequently the hip, knee, fingers, and feet. It may be idio- 

 pathic, or due to rheumatism or to injuries, or follow an acute arthritis. 

 The capsules of the affected joints are thickened and sclerosed. The 

 synovial fluid is at first increased in quantity ; later, diminished and 

 thickened. The tufts of the synovial membrane become much enlarged 

 and vascular ; they may be converted into cartilage. Sometimes the cap- 

 sule becomes ossified. The new bone grows from the edge of the carti- 

 lage within the capsule and its articular surface is covered with cartilage. 

 The articular cartilages are much changed. The basement substance 

 splits into tufts, while the cartilage cells are increased in number. Or 

 the basement substance becomes fibrous ; or it is split into lamellae and 

 the cartilage cells are multiplied ; or there are fatty degeneration and 

 atrophy. 



As a result of these changes, larger or smaller portions of the cartilage 

 are destroyed and the bone beneath is laid bare. The exposed bone may 

 become compact and of an ivory smoothness. The ends of the bones are 

 much deformed. They are flattened and made broader by irregular new 

 growths of bone, while at the same time they atrophy. The new growth 

 of bone starts from the articular cartilages. The cartilage cells increase 

 in number and the basement substance grows in quantity. This growth 

 is most excessive at the edge of the cartilage, so that a projecting rini is 

 formed there. This projecting rim may ossify next the bone, and at the 

 same time new cartilage may form on its surface, so that we may find 

 large masses of bone covered with cartilage. All these changes occur in 

 various combinations and sequences, so that joints in this condition pre- 

 sent the greatest variety of appearances. 



Arthritis TJritica (Gouty Arthritis). This lesion is characterized by the 

 deposit of salts of uric acid in the cartilages, bones, and ligaments, and 

 also in the cavities of joints. The deposits may be in the form of stellate 

 masses of acicular crsytals in and about the cartilage cells or in the base- 

 ment substance ; or they may be deposited in the fibrillar connective- 

 tissue structures of the joint in single crystals, or in the subcutaneous 

 tissue about the joint as white concretions. The deposits may occur in 

 repeated attacks of the disease, and are accompanied by acute inflam- 

 matory changes. They may lead to various forms of chronic inflamma- 

 tion of the joints. 



Tuberculous Arthritis. This process may commence in the joint itself, 

 or may extend to it from adjacent bone. It is characterized by the for- 

 mation of tubercle tissue and granulation tissue, sometimes in great quan- 

 tity, and is usually associated with secondary inflammatory and degener- 



