ETIOLOGY AND OCCURRENCE 21 



Certain ligaments are subjected to strain more than are others 

 and therefore, when so involved, frequently cause lameness. Ex- 

 amples of this kind are affections of the collateral (lateral) liga- 

 ments of the phalanges. Because of the leverage afforded by the 

 transverse diameter of the foot, when an animal is made to travel 

 over uneven road surfaces, considerable strain is brought to bear 

 on the collateral ligaments of the phalanges. A sequel to this 

 form of injury is a circumscribed periostitis at the site of at- 

 tachment of the ligaments and frequently the formation of an 

 exostosis — ringbone — results. 



Where sudden and violent strain is placed upon a ligament 

 and rupture occurs, the division is usually effected by the liga- 

 ment being torn from its attachment to the bone. In such cases, 

 a portion of periosteum and bone is usually detached and the 

 condition may then properly be called one of fracture. In some 

 cases of this kind recovery is tardy, because of the difficulty 

 in maintaining perfect apposition of the divided structures, and 

 reactionary inflammation is not of sufficient extent to enhance 

 prompt repair. In fact, some cases of this kind seem to progress 

 more favorably, when no attempt at immobilization of the af- 

 fected member is attempted. 



If some freedom of movement is allowed, acute inflammation 

 resulting in nature's provisional swelling soon develops and 

 repair is hastened because of increased vascularity. But where 

 luxation of phalanges accompanies sprain, reposition and immo- 

 bilization are necessary — that is if cases are thought likely to 

 benefit by any treatment. 



Luxations — Dislocations. 



Luxation or dislocation is a condition where the normal rela- 

 tion between articular ends of bones has been deranged to the 

 extent that partial or complete loss of function results. When a 

 bone is luxated (out of joint), there has occurred a partial or 

 complete rupture of certain ligaments or tendons; or a bone 

 may be luxated when an abnormal or unusual elasticity of inhib 

 itory ligaments or tendons obtains. 



Luxations may be practically classified as temporarij and fixed. 

 In temporary luxations, disarticulation is but momentary and 



