Certain ligaments are subjected to strain more than are others and therefore, when so involved, frequently cause lameness. Examples of this kind are affections of the collateral (lateral) ligaments 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 attachment 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 ligament 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 affected 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 immobilization 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 relation 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 inhibitory ligaments or tendons obtains. Luxations may be practically classified as _temporary_ and _fixed_. In temporary luxations, disarticulation is but momentary and spontaneous reposition always results; while a fixed luxation does not reduce spontaneously but remains luxated until reposition is effected by proper manipulation and treatment. Fixed luxation may be of such character as to be practically irreducible because of extensive damage done to ligaments or cartilage. Where a complete luxation of the metacarpophalangeal joint exists, it is probable that in most cases sufficient injury to collateral and capsular ligaments has been done to render complete recovery improbable, if not impossible. Temporary luxation of the patella is a common affection of the horse and fixed luxation of this bone also occurs. As a matter of fact, in the horse, patellar luxation is the one frequent affection of this kind.