DISEASES OF ARTICULATIONS 199 



Deforming Arthritis (Arthritis Deformans). 



What is arthritis deformans ? 



It is a chronic aseptic arthritis characterized by a perma- 

 nent and material change of the shape and structure of a 

 joint. 



What are its causes ? 



Usually a traumatism, as contusions or distortions. Her- 

 edity — that is, a predisposition to it — plays an important role; 

 chronic articular rheumatism. 



Describe the changes talcing place in arthritis deformans. 



The disease usually starts in the articular cartilage. The 

 cartilage cells proliferate, thus robbing the cartilage of its 

 firmness. At the point where the articular surfaces come in 

 contact — that is, rub each other — the cartilage is ground down 

 more and more until eventually the epiphyses of the bones 

 tench each other, the balance of the hyaline cartilage — that 

 is, that portion not in actual contact with each other, but 

 more or less free at the margin — also proliferates, forming 

 excrescences. That portion of the periosteum covered by the 

 synovial membrane where the latter is fixed to the margin of 

 the joint also undergoes inflammatory changes by contiguity, 

 as the result of which subsynovial exostoses are formed, read- 

 ily seen or felt, and according to their location variously 

 termed spavins or ringbones. The synovial membrane may 

 in time become thickened as the result of the inflammatory 

 process, this being especially the case at those points where it 

 is fixed to the articular margins. Inflammatory changes, 

 such as thickening of the connective tissue ligaments about 

 the joint, as well as an ossifying periostitis, may become a 

 natural consequence of the inflammatory process originally 



