DISEASES OP AETIOULATIONS 205 



iQive a common exam,ple of periarthritis. 



Periarticular ringbone, taking its origin from the point 

 of insertion of the lateral ligaments of the first interphalan- 

 ^eal articulation. 



Mxplain the nature of a periarticular ringbone. 



This form of ringbone is the result of a primary chronic 

 ossifying periostitis produced by a tugging upon the lateral 

 ligaments of the joint, such as follows faulty positions of the 

 limb, for instance, in contrast to true articular ringbone, 

 ~which starts either as a primary osteitis or occasionally as an 

 arthritis deformans, showing that there is a marked difference 

 between articular and periarticular ringbone. 



Ijuxation of a Joint. 



What is luxation f 



A permanent separation of two articular surfaces from 

 ■each other with partial or complete laceration of its liga- 

 ments. 

 What is a subluxation ? 



A partial or incomplete dislocation ; that is, the articular 

 «nds are more or less in contact with each other, the liga- 

 ments being rarely torn. 



What is a simple, what a complicated luxation ? 

 , In the former there is no serious damage done to the sur- 

 Tounding soft parts or the bones, the articular ends are not 

 exposed to the air ; while in the latter there is serious injury 

 of soft parts or bones, as, for instance, a fracture, the articu- 

 lar ends being in contact with the external air. 

 What is a recent, what an old luxation ? 



The terms recent and old in this instance are not sug- 

 gestive of the time passed since the accident, but indicate the 



